I spread it out a bit. When I level up, I clean up whatever vocab was left of the previous level and get to the radicals but no kanji. I’m only worried about getting that first review of radicals right (because getting them wrong will probably slow the level down). Once the first review is out of the way I’ll pick up whatever kanji I can, then slow down and clean up the rest of the vocab over the next couple days.
For me, the goal is to have done all the vocab lessons before the first set of kanji reach Guru, then do all the vocab lessons again before finishing the level. It keeps a steady flow of lessons without front-loading them all at the start of the level which makes for big spikes of reviews down the road. My method still front-loads a bit because of all the extra vocabulary from the previous level before I get to radicals, which is often 20-30 vocab words. Using a reorder script would streamline this a bit more but I like it the way it is.