Welcome aboard!
So which Savage 338 LM did you get?
One of my 338 LMs is a 110 FCP-HS.
I use H1000, RL26 for the 250's , and RL33 for the 300's in my 338 LM.
Then there's also Retumbo, N570, US869, there's actually allot of them.
Really, any of the slow burners can work, and unfortunately, there's just no shortcut to that magical formula. Especially when just starting out. (You could get lucky and hit it right off, it's been known to happen.)
The powder that works best in your rifle with your bullet and components will be "the best".
The "pressure" you mention is controlled primarily with how much boom dust you put in your case.
This amount will vary by all kinds of stuff, really. Chamber and case volume, where you seat your bullets, the interior dimensions of your barrel the exterior dimensions of your bullet (mostly weight and bearing surface) even which primer you use can have an effect. Hint: use Federal 215M primers.
If you're looking for just one powder, maybe start off with H1000 or RL 33 and see if one of those get you where you want to be.