You don't necessarily want the highest velocity, you want the one most suited for you needs.
If you want just one powder for all four of those bullets, I might guess you are looking for flexibility and economy above accuracy or all-out speed.
Varget is a very flexible powder. You could look up the loads for those cartridges to see the recommended loads for them. I tried Varget out and it worked well for 55g .223 and 150g and 168g .308. I currently use H335 (commercial version of WC844 military powder) for both 55g .223 and 150g .308.
Fortunately in your case, if you want to load 125g 30 cal bullets along with .223, you will have more options than if you were to want to use 150-175g 30 cal bullets.
You should check out H335, IMR 3031, Win748 or Ramshot TAC for powders which can be used in lots of different cartridges.
As a reference
From the Hodgdon reloading site:
7.62x54R:
125 GR. SIE SP Hodgdon H335 2.715" 50.0g start 2997fps 36,500 CUP 53.0g max 3193fps 45,100 CUP
125 GR. SIE SP Hodgdon Varget 2.715" 51.0g start 2967fps 37,400 CUP 55.0g max 3139fps 45,700 CUP