I can't really help with which one, as I haven't had enough experience with either model. So go whichever you feels is best. As far as max loads go, in all honesty most shooters don't use 150 gr loads. Reason being accuracy loss is common. A 100 gr with 240-300 gr load will drop a deer to 200, if the hunter can. Like mentioned stick with what the manufacturer suggestion and when increasing do so by small margins of 5 grains with loose powder. If your going to run pellets than start out with 2x50's = 100 with different projectiles in the 240-300 gr range. If you want to experiment higher buy some 30's and make other combinations till you reach optimal performance or max. I personally would never take a new rifle or Ml out of the box and jam it up hot, work it in slowly.

Personally I'd scope it, but choice is yours.

IMO SS is better for new mler's, reason being easier to determine the entire rifle is indeed clean. Not just the bore needs to be kept clean but rather the entire rifle. SS is just a tad bit more user friendly in this regard.