Descender means you lose the remote. But, the upgrade kit is £60ish inc postage from GD, which is more than just getting a Turbo in the first place but not the end of the world. And fitment since it's a gravity dropper is dead easy. Still, best do it right first time…
Get the 4 inch drop… No reason not to IMO, 3 inches is usually enough but I doubt you'll ever think "Oh I wish I had 1 inch less drop".
Multidrop gives you a setting in the middle, so you can have 1 inch drop for "cruise". Which is a good idea but it's a bugger to get it to click in at the small drop. Mine doesn't have it but I tried it on a mate's and I could only get it about half the time. He has trouble too, it's not just me being a mong…
You can add multidrop yourself, all it is, is a hole drilled in the post. Apparently. Not done it myself so if it snaps in half, don't blame me 😉 But, I figure I'll stick one in the middle if I do, easier to find with my non-precision arse. Might just not bother.