How many kanji you do at a time depends largely on what your goals are. Are you trying to go as fast as possible? are you going more for leveling up every 8 days? 10 days?
Check out the huge guide on this post: My Journey of 368 days (+ The Ultimate Guide for WK 📖 )
Particularly look at sections 4, 5 and 6, in which he talks about setting your schedule and finding a speed that works for you. He also discusses how leveling up works so that you can gain a better understanding of what things you need to do, and when to do them, in any given level.
Edit: as you get into later levels, your level ups will start to unlock 80+ lessons at a time, and it simply isn’t feasible to do 80 lessons in a day and actually learn something. So I would not recommend doing all your lessons as soon as they unlock. Even if you are only considering the Kanji, some levels will unlock 20+ kanji on level up, which is a lot to learn in one sitting.