I would think a full size mattress would be the be the best fit for both. Because the mattress will be thinner than a standard mattress it shouldn't matter that the length comes up a bit short. You can just tuck the excess under the mattress.
Full is probably the closet, as the diagram indicates. Camper mattresses are not the same as home ones, especially for popups. The mattresses tend to be thinner than home ones, even with toppers added.
Some end up using sheet garters to help hold them in place. Some use jersey sheets, sometimes in the next size smaller - I never tried it, so can't say how well it works.
Blankets are probably OK in that size too. It gets interesting with the one long side against the canvas (for these size mattresses. with some of the larger ones, one can sleep either E-W or N-S) and head and foot at the canvas too. In our popups, we just bought a mattress pad sheets in the closest size. Our blankets have been mostly remnant Polartec ones, and I made quilts to fit.
I went the route of jersey sheets in a size smaller. The fitted sheet works quite well Surprisingly. Because these sheets stretch (like a T-shirt material) i was able to stretch the ends over the mattress. Downside, they aren’t very comfortable on a hot summer night (too warm) and if it’s really humid outside the sheets tend to feel damp even if they aren’t. I bought a size smaller in blankets so I don’t have a ton of bulk to tuck however downside to that if you have a partner that likes to hog the blanket the other partner will have nothing. I sometimes opened a sleeping bag all the way up to use as a top comforter I used two bags when i slept with the blanket stealing kiddo. Bonus, Sleeping bags could also be used like a regular sleeping bag especially if it gets real cold. When I was growing up my brothers had to share the back bunk on our popup. They argued a lot if they had to share blankets so mom sowed a Side up on a folded sheet to create like oversized light weight sleeping bag for each. Combined with their own twin size comforter they were more content.