I don't have any photos of the net tent packed away in its stuff sack but as I recall, it doesn't pack down quite as small as the Trailstar itself.
As far as modifications go, the only thing I've changed or done to my Pentanet was added mitten hooks to the guylines so that I could then attach the pentanet guylines to the (staked) Trailstar guylines instead of using separate stakes for the pentanet. This is nice for saving some weight but makes adjusting/tightening the guys on the pentanet a little more tricky.
When I originally ordered the pentanet, I discussed the idea with John at BPWD of adding hooks or loops to the ridge seams, halfway up the sides of the innernet shelter so that I could attach these hooks to the underside ridgeline hooks on the Trailstar (to open up more interior headroom sapce inside the net tent). I didn't end up doing it because they would be difficult to (un)attach when everything is set up, but I still think about it sometimes because you do lose some usable interior space inside the Pentanet from the walls sagging in if you don't pitch the innernet shelter high and tight enough (during a lower storm pitch, for example).
I've haven't experienced any problems with condensation inside the net tent. There's a pretty good amount of space inbetween the TS and the net tent for the most part. Plus the Trailstar pitched up off the ground a little bit allows for pretty good air circulation.
As far as choosing between the designs, I think it comes down to what you're looking for. For my purposes, I needed to maximize interior enclosed space to have all the room I can get to fit myself, my girlfriend and our dog (it's the girlfriend's requirement to have an enclosed space in the first place, when I go without her I leave the innernet at home). If you don't need to max out enclosed area and retaining some vestibule space under the Trailstar but outside the net tent (for cooking, for example) is more important, then perhaps the pyranet design is better for you.