Grammar is nice in that everyone can do it at their own pace. I’m personally a slow and steady type but speed-demons aren’t necessarily doing anything wrong either. I would say with Genki that you probably aren’t flying through merely because of your kanji level though because Genki does not heavily rely on kanji to get its grammar points across to.
My advice to you is to do the first read through however quickly you’d like, but then review a set number of grammar points in depth every night. I think everyone needs multiple exposures to really set grammar in stone. As I have learned from Bunpro, the devil is in the details even if you think you really know something!