Depends on what sort of energy you're looking for. Somebody, somewhere, sometime ago suggested a 1,000 ftlb energy for whitetail. I seem to remember some states regulating handguns for whitetails to 500 ftlbs energy. About .357 Mag levels. Just parameters to start w.
I think today's better bullets and accuracy make lower power less of an issue. I believe the barnes TSX & TTSX are one of the best performing projectiles out there. On our tough hogs, I've seen 223 barnes perform better than I could've imagined.
Anyhow, if you load Barnes 120g TSX conservatively into 6.5 Gendel, and Rem .260, here is what you can expect:
16" 6.5G muzzle=2300fps,1,400ftlbe, 1,000ftlbe=200yds, 500ftlbe=500yds
16" .260 muzzle=2,650fps, 1,900ftlbe, 1,000ftlbe=300yds, 500ftlbe=650yds
24" .260 muzzle=2,980fps, 2,360ftlbe, 1,000ftlbe=450yds, 500ftlbe=800yds
Looks like they would all meet your requirements as an adequate 200yd hunting rifle and longer-range target rifle.
As for target shooting, it depends on how far out you want to play. The .260 will allow you to use the heavier 6.5 projectiles that give you the much higher BCs (ex:Hornady 140g AMax=0.585BC will stay supersonic to 1,000 yd from a 16" .260). The Grendel just doesn't have the case capacity to launch the better BC bullets at the higher velocities they need to reap the BC benefits they are capable of. Using the heavier, higher BC target bullets, the 260 is easily a fun 1,000yard gun. I don't think a 16" Grendel would do that.