Kanji vs Vocab advice?

You can check, but it does max out at some point. It’s not like at level 50 you’ll be getting 300 new vocab items or anything like that.

In my opinion, no. You read and speak with words, not kanji. So knowing the kanji only doesn’t help very much in the long run.

Only if you want to go faster. But as I already mentioned, it’s not worth doing that if you plan to use it to skip vocab. If you do want to use a script to optimize lessons, I recommend [Userscript] WaniKani Lesson Filter. You can use this to choose how many lessons of each type you want to do at any given time. This means that you can do all the radicals right away, and then mix new kanji and vocab together if you want. As long as you do about 3 times as many vocab as kanji, you should be able to keep up with all your lessons.