I just had a custom rifle
built on a REM 721 Repeater and did a REM 700 myself, both repeaters converted to single shot.
For hunting accuracy I doubt that any accuracy difference will be notices. The limitations for a repeater come mostly from magazine considerations when can restrict over all cartridge length which was the reason I went the single shot route.
For hunting its always nice to have a second or third shot with little or no hassle.
Regarding mounts, I've used two piece and solid mounts and haven't noticed any difference in "hunting" accuracy. Having said that both of these rifles out shoot any of the REM 40X single shot benchrest rifles I've ever had. They even out shoot a Hart sleeved Hart barreled 222 that wasn't actually a bench rifle but was converted into one.
You may wish to consider contacting several of the smiths on this board for some considerations.
It sounds like you have a good start.....