This is really a matter of what would work best for you.
I don’t use either, personally. However, I’ve looked at them, and if I were to chose one, I would chose KameSame. I like it because of the additional features, and because it gives hints for words whose translations are synonyms.
When to start using one?
I can’t really answer this question, unfortunately, because I’ve chosen at WK Lv. 10, to start building my own deck of mined vocabulary with Anki. However, I’m still only working on recognition within the SRSs. Instead, I work on production with HelloTalk, since I’ve done around half of Genki book and much of Cure Dolly.
But, of course, that’s only what works for me. You should find what works for you.
I use both, but I prefer KameSame, as it’s more forgiving for words with the same meaning. I use it for all WK vocab, but have it sorted by lowest % correct, so my potential leeches come first. It may go against the theory of SRS to do everything 3 times, but it seems to suit my way of learning.
Wanikani won’t teach you all the vocab there is for the kanji you learn.
A lot of these are actually common words, so when I encounter something like 見本 (Not on wanikani), I add that to kamesame. Since I already know the kanji in depth, it makes the reviews really easy to get through while still widening my vocab!
If you want to add words form wk, maybe add words you constantly struggle with. Adding burned items doesn’t sound like such a bad idea either.
I can recommend KaniWani. Remembering English to Japanese just doesn’t come without a conscious effort, and I have found that I often have a whole different set of mnemonics for that process. I have been using KW without any adjustments since I was at level 4 on WK, and it has definitely made a difference.
BUT… it’s a lot of reviews. When you get into higher levels and some items start coming back, review piles can get pretty high. Think about doubling that number (WK and KW) and it can be daunting. If I was going to do it again, I think the strategy of only using it for items that have been burned on WK makes sense. On the other hand, if you are just starting out, it might be some months before you start burns.
