I have a 300 sbr and here are some of my takeaways and observations.
I didn't hide the suppressor under the hand guard. my can is a sico SpecWar 762 which has a collar that needs to be turned to secure. so, unless there was a gap in the the rail/hand guard, I wouldn't be able to secure the can to the barrel. also, suppressors get hot and I don't want to be forced to use an oven mit when I shoot.
there have been a lot of studies to determine ideal barrel length for 300. current thinking is 9 to 10.5". I believe that Daniel defense, noveske, and advanced armament are all running either 9" or 10.3" as their standard shortest barrel. this is from memory so I may be mistaken. I went with an 8" or 8.5" cmmg barrel because it was steal. I haven't taken any mid-sized game with it yet, though.
I haven't and probably won't hunt with subsonic rounds. I don't think they are as effective at killing deer quickly and humanely. all bets are off for feral hogs, though.
I can't remember the twist rate of my barrel. I think it's 1x8 but who knows? it seems to shoot a wide range of ammo effectively with decent accuracy. I'll probably never shoot this beyond 200 yards with any ammo - sub or super - so sub moa was never my intent.