Personally, I dont really see the point of chopping the frame, but if its something you want to do, hey, have at it. I carry a 17 year round, and dont have any troubles doing so. They really arent "big" guns, and conceal well enough as they are.
As far as "shootability" of the smaller guns, I have a couple of 26's as well, and they are just as easy to shoot as the 17's. I doubt youre really going to see a whole lot of, if any, difference between them.
The one thing I will recommend is stippling, and that goes for any of them (well, except for the RTF2's). The improvement in how the gun feels in your hand and how it shoots, especially with sweaty hands, is pretty dramatic.
Stippling isnt hard at all to do, and if youre the least bit handy, you can certainly do it yourself. All you need is a soldering/wood burning pen and some time. If you have a Glock field knife, they make a great piece to practice on, as the plastic on them isnt really much different than the pistols, and the knife can certainly benefit from the stipple job itself. Ive done a bunch of both pistols and knives now, and have a couple more I plan on doing over winter layoff. I just follow the natural lines of the gun, and dont mark anything out. Start with areas you want done the most, and see where it goes from there.
“The enemy is anybody who's going to get you killed, no matter which side he is on.”
― Joseph Heller, Catch-22