My $0.02 is
I have 2 Savage model 12 FV rifles. One in 223 and one in 6.5 CM. One has a 2 piece base one the other has a one piece. I shoot targets mostly and is is a bit easier to load the chamber one at a time in the rifle with the 2 piece mount. Either will be fine just the 2 piece is slightly easier to get my fingers where I want the to load or grab the extracted round. I like one piece mounts with the idea it's one piece for some reason but either will be fine. Just get high quality parts. They don't have to be expensive just well made and robust.

I bought another Savage Stevens and bought it also in 223 for the same reason you questioned. I do now wish in some ways I would have gotten it in 22-250 because I don't have one. Shooting 200 yds the 223 will be a great choice. You will be very pleased with your rifle.
KYhunter