I am looking into getting a bigger turbo (gt28rsr) but not sure what to do so need some advise from the big boys

i currently have a very good gtir which is making about 270-280 bhp, i know it could make 300bhp with a live map quite easy, but it would be getting to the end of its efficiency. I want about 310-320 bhp but quite reliable as its my daily driver. I love the kick the gtir gives but can break traction to easy when it suddenly kicks in.
I think with a rsr i will have smoother power and it won't be working no where near as hard as the gtir would be at the same power. And if wanted to go forged or more power the turbo is there to do it.
I have afew questions about the rsr if anyone knows them.
-what rpm roughly does the rsr spool with no head work
-Is it ok to run this turbo with stock internals (not silly boost though)
-does the stock water pipes fit onto the rsr easy
-will the gtec2 run this turbo at 1/1.1 bar until i get the money for a live map (will get it checked on rollers for fueling etc when fitted anyway)
-i have a 2.5" h&s dp which is v band, would it be best to weld a 5 stud flange onto that (do i need the deeper flange to clear the wastegate) or get a 5 stud to v band adapter (easier)
I have all the other supporting mods, intercooler, walbro, wiring mod, sip, apexi, boost controller, decat etc
If there's anything else i might need, i know i will need the other parts for the rsr to fit my oil ways etc.
Any help will be greatly appreciated
Ash