I have a custom set-up from Porcelain Rocket that I love. It was made for my 29er, but my 29er's frame geometry is similar to a road bike and I run drops.
I went with a full frame bag with that kit, but after some self-discovery I realized I prefer a partial frame bag with access to my bottle-bosses. A full frame bag gets all tight and corner-y at the bottom of the triangle and I just don't feel like I put that space to good use.
A handlebar bag that fits inside your drop bars is great, but the weight will be high and will effect steering so you need to keep its contents light if agility is a concern. I prefer a harness "sling" type bar bag set-up, because I think it is easy ... all you have to do is detach the dry bag and you have all you stuff as opposed to playing with all the frame/handlebar attachment points. Plus if you get one with foam spacers you can still use the flats of your bar. Webbing along the sling is good too for lashing a wind breaker or shell as you adjust layers throughout the day.
I personally do not like to tour with aero bars. The additional weight of my gear just makes the aero position seem too unstable, but I frequently see them in other peoples set-ups. I run Salsa Woodchippers and I feel like they give me plenty of grip options without compromising space for my handlebar bag, which is the middle-ground I want.
A small top tube bento box style bag is good for phone, SPOT, snacks etc, but I also pair mine with at least one Revelate Designs Mountain feed bag. Otherwise the capacity for "at-hand" snacks seems too pithy. I also use a small "gas-tank" top tube bag back in front of the seat-post for my repair kit and tools. I like to have that kit separate and organized for painless access when I am angry and cursing at my stupid broken stuff.
I hear people talk about stability issues with seat packs, but I have never had a problem and I usually tour off-road with rough terrain. I think the problem comes down to weight. If you are on BPL, I assume your gear weight is in check, in which case you shouldn't have issues with over-weighting the seat-post mounted bag. (Volume and capacity is where most issues arise.) Whatever weight you do load into the seat-tube bag should kept back toward the post.
Sometimes I also use small fork mounted bags in modified Salsa Everything Cages (modified because they always break), but I personally don't like much weight up front on the fork. That just comes down to personal riding style and the type of terrain you are riding. If you do put weight up front, try to keep it as low as your gear and the terrain will allow.
For a short trip, or particularly a front-country trip with regular access to resupply you should definitely be able to get away with just the packs on the bike. For longer unsupported tours, volume tends to be the killer. In those cases I wind up using use a pack for my food, happy in the knowledge it will get lighter as I progress. I have a Wingnut Gear Enduro that I love for this purpose.