Your thinking through this correctly. Leave the insulated bibs at home for PA whitetail sits and bring more "technical" style tops and pants with long underwear. Avoid cotton socks (get a few pairs of merino Darn Tough over the calf heavy cushion hunting socks and thank me later) and underlayers and invest in either merino or sythetic. Merino will keep you warm even when its wet with sweat, but you need a wam, dry, place to dry it out for the next hunt. Merino can also be worn several times before it starts to stink. Synthetic doesn't have the same insulating properties, but dries out much faster. However, synthetic does tend to trap odors worse than wool.
I hunted the Big Horns last fall in mid-October for 8 days. The first couple days it was in the 40-50s and then it dumped a foot of snow that remained the remainder of our 6 days of hunting. The temps. also dropped into single digits at nights and teens/low 20s during the day. The one thing I would recommend (that I didn't have) is a packable puffy coat, super warm hat, and extra warm glomits or mittens, for glassing sessions. Ditch them when you're moving around, but have them in your kit if you're going to be out for days at a time. Also, if you don't have any yet, get some trekking poles. My buddies had these and I didn't, and for steep inclines/declines both they are clutch and save a lot of wear and tear on the body.
Good luck!