Simple put, your asking us when your rifle will tell you what it likes.
For the 300 RUM, great bullet choices would be the 210 gr SMK, 210 gr Berger or 208 gr A-Max. These are three of DOZENS that would work well for the ranges you list.
For the 270 WSM. Not as many great choices for bullets. The 150 gr berger is a good solid choice as are the 165 gr Matrix but again, your rifle is the one that will tell you what it likes best.
Use load data that is listed out there, there are loads of it for both chambering.