I know from your posts that you're a highly experienced hiker who can handle the High Route without a problem. (You may even find the navigation much easier than some of what you're used to; most everything is above treeline and is line-of-sight.)
NOBO is my preference. I've done some of the trail southbound, and it was tedious to read Roper backwards.
Get thee Andrew Skurka's mapset. Additionally, if you deviate from Roper at all, you may need a few 7.5- or 15-minute maps to supplement the Skurka maps. Also get the book, High Sierra: Peaks, Passes and Trails by Secor. Secor offers detail on certain passes, an alternative viewpoint to Roper's. I walk with some xeroxes of pages from Secor's book, and/or have the Kindle version on my phone to pull out and read when scoping out the next day's passes.
Personally, I would pick a starting point and not get attached to a certain pace/ending point. It's not so much that I think you'd overestimate your ability or speed (I'd have that concern about many people but not about you). More because there is lots to see and enjoy along the way. What I really wish I'd done is make more time to stop at the truly jaw-dropping places on the Roper Route, drop my bag and explore for a half-day, or do a full-day side trip. Rather than just rushing through Paradise to the next thing (the "next thing" often entailing the rejoining of a dusty trail somewhere). More on some good side trips later.
1. Agreed that the better starting point is Kearsarge Pass - or, even better to avoid the Kearsarge/Rae Lakes crowds, start at Taboose Pass Trailhead. An eastside entry offers MUCH easier logistics! From the intersection of the Taboose Pass Trail and the JMT, head northwest over Cartridge Pass into Lakes Basin, where you join the SHR. Spend some time in Lakes Basin before rushing on.
2. Thunderbolt Pass instead of Knapsack Pass. It is simply more beautiful. Also, it gets you closer to Bishop Pass, a convenient resupply pass. Send a package to Parcher's Resort, just a couple of miles north on the road from the South Lake trailhead.)
3. Alpine Col instead of Snow Tongue Pass. The latter is just plain suicidal. Secor book will help you get over the Alpine Col.
4. From Deer Lakes, just before Mammoth: The off-trail segment into Reds Meadow is awful. Not too scenic; slog through burnt forest. The only reason the High Route goes through here is that, well, it's trying to get you to (ugly) Reds Meadow for resupply. Instead, just take the darn trail to Lake George. From there, grab the (free) shuttle into Mammoth for resupply. Rejoin the SHR by taking the (other, paid) Mammoth area shuttle to the Devils Postpile area.
5. From that valley (Reds/Devils Postpile/Agnew), skip the part of SHR that goes to Beck Lakes. (Again, just not the most scenic by SHR standards.) Instead, rejoin the SHR either at Minaret Lake (via Minaret Lake Trail out of Devils Postpile); or at Ediza Lake (via Shadow Lake Trail out of Agnew Meadows).
I don't think I could bring myself to miss the SHR north/west bound out of Lake Catherine. Twin Lakes, Bench Canyon, Blue Lakes: That is a positively amazing area. Sure, from Blue Lake Pass to Tuolumne Meadows looks like a lot of trail miles, but the first half of those trail miles is along a rarely-traveled corridor (especially by Yosemite standards). I do not think we saw even one person on that corridor. It is in Lewis Canyon (?) just south of Vogelsang where you will start encountering people, but those are also very fast, easy trail miles that you can dispense with quickly. The alternative - the Lyell Canyon approach south of Tuolumne - will be just as crowded.
Someone has already mentioned some interesting peaks. Mount Sill (a day trip from Lake 11,676 on the SHR north of Palisade Lakes) is rumored to have the best view of all the peaks on the route. Even if you don't climb Mount Sill, try to camp about a mile off the SHR on the eastern or northeastern shore of Lake 11,676. I think my best photographs in the Sierra are from this little-trampled spot. And yet most SHR hikers miss this view, because they pass the west side of the lake instead. To reach the east/northeast side of the lake, traverse along its north (not south) shore.
I think there are several lakes not to miss. I have already mentioned Lakes Basin. Most people say they are kicking themselves for not finding a whole day to spend exploring that huge basin.
From near Muir Pass - Helen Lake or Wanda Lake - drop over into Ionian Basin for a day or two of exploring the moon.
I'm told that the Bear Lakes basins are worth stopping to explore. As is Vee Lake, to their southwest. I am planning a trip to this area myself this summer, and don't have the fun recon yet.
On the Silver Divide, Grinnell Lake is a photographer's favorite, and is said by some to be their favorite lake just a mile or two off the SHR. If you go there, consider continuing directly over Pace Col (see Secor) to Red and White Lake. On the north side of the Silver Divide, the hundreds of little lakes and ponds are pristine, full of birds, surrounded by the brightest granite you've ever seen, and not worth rushing through! You might want to drop your pack for another half-day exploration, to lakes such as Hortense.
Next, you are spit out onto the JMT for a few miles. Avoid camping at the too-popular Virginia, Purple, or (outlet of) Duck Lake. Instead, go for a pond off-trail above Virginia Lake; or to Pika Lake or Deer Lakes.
Alternately, if you have spent days exploring and are low on supplies, exit the Silver Divide via Tully Lake to the McGee Pass Trail and out over McGee Pass. That is a much nicer trail than the JMT in that section. Not heavily traveled. From McGee Pass Trailhead it is pretty easy to hitch to Mammoth for resupply.
From Lake Catherine, Ritter Lakes are worth exploring. It is extremely rugged, and you may have trouble finding a place to park your tent. From the farthest (southernmost) Ritter Lake, I believe, you can find the easiest way to summit Mount Ritter.
From the northernmost of the Twin Lakes, take a day to explore the big basin above (to the north). The geology in that basin is just out of this world. There are entire rock walls full of fossils. It is like nothing else I have seen anywhere in the Sierra.
However far north you get in x days: Exit an eastside trail and hitch back to a town along the 395 corridor. Yes, there is a daily bus that runs up and down the 395 to Reno. I think you can do this whole trip via bus + hitchhike. If you need to get from Bishop to the Taboose Pass trailhead, a little-used spot, you may need to hire a shuttle out of Bishop. If you're worried about being a smelly hitchhiker, take note that there are shower facilities at or near most eastside trail exits. You just need to look around or ask. Often it's a resort or an RV park a couple hundred yards down the road from the trailhead.
If you do have a car, consider leaving it in Bishop. Thus, it will be easy to bus or hitch back to at end of trip. Don't leave it in Mammoth: There is a big bear problem there, and no bear boxes to store you food in, and so the bears WILL break in to your car.
If you have any equipment needs, the best outdoor stores are in Mammoth and Bishop.
My biggest piece of advice is to post your question on the High Sierra Topix backpacking forum. That is the best collection of experienced x-country Sierra hikers that you will find anywhere. They will have much in the way of pointed and specific guidance. In particular, these people have amazing recon on the trickier passes - Cartridge Pass, Alpine Col, Sky Pilot Col - the kind of detailed info you will find in NEITHER Roper nor Secor. Additionally, High Sierra Topix has a climbing subforum, and on there you will find detailed accounts of how to climb peaks such as Mount Sill, should that be of interest to you.