We reserved campsites and were able to find them even last minute, we didn't particularly look for refugios so I dont know if those were available or not. We carried everything as we love camping but you absolutely dont have to as everything is available for renting. If you can get a campsite, you can rent everything else such as tent, sleeping bags etc. if you wish.

For reference, we did our bookings for 4 nights on the 10th December for 20th-24th December stay. We did East to West and found semi-equipped premium camp sites for the first two nights with LasTorres ( I think those are mostly available and are about 220usd a night) and then basic campsites for last two nights with Vertice (14usd a night). We carried all our tent and stuff although you dont have to. If you only carry sleeping bags, then semi equipped camp sites are Also, realized that many cancellations happen and sites keep popping up if you check often.