Im mainly a sidearm driver. I dont ever release at a 90 degree angle from the ground. Its gotten to the point where i get so much torque on the discs, that they all turn understable for some of their flight. Id say I throw most of my long distance drivers somewhere between 30 and 40 degrees down from a hyzer angle.
I carry several weights for a couple of discs, both work slightly different from the same release angle. My 168 Orc actually turns understable, and flexes out. It'll go fairly straight down a long fairway, but it'll make the path with a slight S-curve. The 173 Orc I have pretty much holds a straight line the entire path, and has a nice soft fade at the end of its flight.
Once you learn what angle to start ripping these drives from, you'll gain a lot of control. A lot of my upshots and approaches are thrown sidearm, because I've been doing it so long that I can guage approach shots 10 times more accurate. But thats just me.
The way I kind of started learning my own sidearm style, was throwing more and more overstable discs for a little while to correct my release angle problems... I didnt get as much distance as I would of liked, but I learned to control em. From there I started going more and more stable, and even to understable discs. Once you get some technique down with sidearm drives, you'll probably start to turn stable discs understable. Sometimes i get a nasty kink in my game for 9-12 holes where I turn my wrist at the last second of my throw, and I end up turning over a disc right away, and it'll just be a wormburner. But once you learn to angle that drive down X amount of degrees, you'll start to really control em off the tee
My backhand isnt the greatest, but it has come a long way. I used to have trouble hitting 300, but now ive gotten enough technique and form to hit 350 max. To me, thats sufficient. I dont feel the need to strive to hit 400 ft at all anymore. Mainly because my sidearms can hit 370 with the right drive.... ANd ive birdied a couple of 390 and 410 foot holes from sidearm skip shots.
My game is at the point now where I try not to rely on my sidearm so much, because I do realize that it is a crutch, and with the right technique I can outthrow it with my backhand.... But I'll still throw it when i need something more accurate.