Lesson question - clear the queue or space them out?

It depends entirely on what best suits your learning style and how much time and effort you can devote to your studies - the answer is going to be different for each individual.

I prefer consistancy, so I have the same number of lesson everyday (11, not 20!, and 1 batch only) - I also use the [Userscript] WaniKani Lesson Filter which allows me to have a combo of 3 radicals &/or kanji with 8 vocab, which gives me even more consistancy since I find the kanji lessons need more brain power than most vocab, so spreading them out right across each level works best for me.

This method, as opposed to keeping lessons at 0, spreads the workload out, and so keeps the review numbers reasonably even instead of getting spikes. The further along you get the greater the workload, so doing all your lessons right away, and dealing with those review spikes could get really hard (burnout :fire:).