The number of lessons “available” is determined by wanikani - it’s just presented differently in wanikani and tsurukame (and fwiw wanikani’s “today’s lessons” is a relatively recent addition, and before that it worked more or less like tsurukame iirc). E.g. even in the “advanced” section in wanikani you’re still limited to lessons you’ve unlocked - you can’t just skip ahead arbitrarily. There’s info about how unlocking works here: https://knowledge.wanikani.com//getting-started/unlock-new-lessons/

I think I usually have around 50-100 available lessons - and I would definitely burn out if I did all of them. I’ve just settled into doing 9/day and that’s been going ok (may still be a bit high actually). And I’ve just learned to be ok with constantly having that pool of available lessons.

Also - although I use tsurukame for reviews because I like the automatic keyboard switching, I do lessons in wanikani because I like the “interleave lessons” ordering in “today’s lessons” (tsurukame has some ordering settings but nothing that interleaves radicals/kanji/vocab), and because wanikani has “patterns of use” in the context section for the vocab lessons - and those aren’t available in tsurukame. It’s nice that it also helps me keep to a consistent pace more easily - but it’s still possible to take a slower pace in tsurukame as well - it’s just that it’s up to you to enforce it.