Haven`t loaded for 6.8SPC cartridge.
H4895 would cover all cartridges mentioned pretty well according to data. And have used H4895 in 223/22-250/243 with good results.
Haven`t seen Varget for sale anywhere in over 2 years here in central Ohio. Went with IMR4064 instead for 75gr VMax in the 243Win.Agree with FairChase93 on IMR4831 on the heavier bullets in 243Win for sure.
H4895 or IMR4895 would be my first pick for mentioned calibers and bullet weights. Certainly a very good choice for many calibers if available.