I could do a summer or early fall overnighter in a 1800 with no spotter or tripod (or with the tripod on the exterior), but I’m pretty compact. Ultralight Thru hikers are routinely doing long distances with packs this size, of course that is without a stove and living off of instant shakes and cold soaked oatmeal. Judging from the average hunter’s pack that I see (guys these days are taking -7,000 size bags out for day hunts for some reason) few hunters can fit into that for an overnighter. -definitely need ultra sub-compact gear: quilt instead of a full bag, tiny stove (if a stove at all) such as a Pocket Rocket, minimal extra clothes, small tarp, UL pad, no luxuries etc.
otherwise, I’d look at whatever the current bag designs offers in the ~3,000 range for overnighters+ with full optics and late season insulation and/or a hot tent.
So, an 1800 overnight for hunting is doable, but not as commonplace as one would expect now that “backpack hunting” has gone mainstream.