Re: .243 barrel length
I think it "too long" of a barrel is dependent on what you want to do with the rifle.
Target/Steel/Varmint doesn't sound like it's going to be slung, shot off hand or even carried far...so if it were me, I'd go for as long and heavy as you can. Stiff, heavy and long doesn't sound like it's a bad thing for your intended use.
If you were going to big game or predator hunt, I'd stick with the 22-24" and maybe a little bit lighter profile.
I'm rebuilding my 243WSSM AR with a 1:8 24" but I'm building a 6-06 on an M70 with a 27" and both of them will be carrying a 9" suppressor. (i know they aren't a strait .243 but it's the same principle)