Wanikani will get you 8000 very useful words. At level 7, the workload has not yet gotten very large. But it will likely get to 200-300 reviews per day. See What level to get 200+ reviews each day? - #16 by bolaurent.
I think you should just stick to wanikani, and meanwhile work on grammar (which wk does not teach you). Soon enough, WK will have you busy enough.