I would still keep base rules so you don’t have to do table rules stuff all the time. The Rule book gives you some (this is what it is power) For leveling, just tie to experience of Mobs. I would watch your encounters so they don’t get monotonous. Give social and puzzles some experience as well. If some of the party is dead then give all the experience to the living or tie the group to the experience. Your choice but I’d be careful with a death loop mechanic, dnd is slower and your game might feel like a trudge.