I have 3 308's. I think my twist would be the standard for the round, 1/10, or 1/12. I forget what the standard twist rate is for the 308. I usually use 165grn bullets. For deer hunting I get by fine with Hornaday 'interlock' type SP's, or Sierra Gamekings.
There are many good powders in the medium/fast range that work well in the 308. If I was to load today I would look to Varget,H4895, or Ramshot TAC. Those are a few powders I like & have on hand.