Re: Powder for 7mm Rem Mag
62.5gr IMR 4350 CCI250, I used to use this load with the Nosler BT. It drives tacks, I don't see any reason that a Partition wouldn't shoot very well with it either.
One powder doesn't necessarily group better than another, it's your recipe, Combo of bullet, powder, primer, cases, seating depth all working together
RL22 is one of the best powders I ever used in my 7mag, I never had any issues at all regardless of temp. H1000 likes a heavier bullet than 150s, 160gr -190gr it pretty well out paces most others with the major exception being Retumbo, Ramshot magnum, and supreme 780 also look pretty good on paper but I've yet to try them. If your worried about temp stability the Hodgdon Extreme powders are the ticket, H4831 being a very very good powder for most bullet weights.
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.