The Whitehorse Wallmart. Ouch, but so true.I'm only a truck camper guy, but you did mentioned my home turf ...
I'm in BC and I don't recall ever seeing a large expedition type truck off highway in BC - okay, might have forgotten one or two. The few we've seen have been on/at the highway, rest stop, or established CG. Seen a few up North: off Dempster, and of course Whitehorse Walmart.
That said, over the years we have encountered lots of industrial traffic off highway in Western & Northern Canada. Five tons, ore trucks, Fat boy log trucks, tractors hauling huge drilling equipment etc. So I'd say yes 35' would be doable on main resource roads and bridge limits wouldn't be a problem.
Where you'll miss out is exploring the side roads - and finding the camp spots, waterfront or view they might access. True, some may have been built for industrial vehicles but they deteriorate, bush in, wash out, are decommissioned, cross ditched etc. Your not gonna drive a 35' rig down those roads billiebob posted, let alone a log truck, for FOTA (fear of turning around) or FOGS (fear of getting stuck)
So you'll likely be on the mainlines and camping with the larger trailers and odd C-class in clearings, staging areas and similar easier access campspots (and I say that knowing some guys will take trailers anywhere they fit). You "could" venture into the bush but whether you will is another thing.
However, you wrote getting away from civilization rather that away from people so a large vehicle should still be good and certainly more comfortable inside than our little camper.
ON EDIT I'll add there can also be a time issue. Guy on a quad will check out every side road 'cause it's fast and fun. The larger, less agile rig might still be capable but will go much more slowly, and there's always those worries... So that side road to explore and maybe find a nice lunch or camp spot could be a 3 or 4 hour commitment. Too many duds and it can become tiresome. It's no wonder folks become creatures of habit and return to the familiar spots.
Having a lot of time and curiosity can change the equation though !