Never fished Holcombe but have spent lots of time on Caldron in the past. You mentioned fall fishing--Sept is still a bucktail/weed bite but I've also done well with twitch baits, bulldawgs and jerkbaits. Early in Sept I use topwaters frequently. Oct is jerkbait, crankbait and live bait time.
As far as spots to fish--main lake structure/points with quick access to deep water. There is one spot I fish absolutely every time I go to Caldron. There's a large rock/weed complex mid lake that's will hold fish year round. You can see rocks sticking above the surface but the complex is large so stay well off the rocks and watch your electronics. Deep weed edge is at 7-8 feet in general. I work a full circle around the entire complex most of the season but hit just the deep water/river channel portion as fall progresses. There are a couple points that duck hunters hunt that can be good also. My viewpoint, if I see decoys I stay well away. There's always another spot I can fish and let the hunters have their spot. In general, Caldron is decent numbers water for the area but it can't compare to the waters in, say, Vilas or Oneida counties. If you want a shot at bigger fish, High Falls is probably a better bet.
As for accommodations, rwl had good suggestions. Also, Gov Thompson State Park has camping available.