@Leebo is right that you might be able to just use WK, but I think RTK has some advantages for learning how to write. For someone who’s not level 60 yet, you don’t have to wait to unlock anything, for one thing. But, more importantly, the way the kanji are broken down is with the purpose of learning proper stroke order. Also, the book demonstrates the stroke order for each kanji. It might seem trivial, but stroke order matters in a way you only come to appreciate once you start writing. It helps your writing flow so much better because it’s such a systematic and consistent way to write. Apparently, from what I’ve researched too, using the correct stroke order helps people read your handwriting better, especially if it’s not the neatest.
A final benefit is that RTK only gives you one English word per kanji and never repeats that word for any other kanji. Since you want to practice writing from memory, you need something to trigger the memory. If you have multiple kanji that have the same meaning, you won’t know which to write when you are practicing.
A potential downside of using RTK for you might be that you might potentially get mixed up since there’ll be conflict between RTK’s stories and WK’s. The same goes for the meanings. You are only given stories for the first 500 kanji, and I mostly use my own anyway, or ones from the site kanji.koohii.com. Perhaps you could use WK’s stories as long as you can adapt them to trigger the memory of how to write the kanji correctly.
Overall, RTK is nice because the system was made with the intention of teaching you how to write. It sort of “teaches you how to fish.”
Whichever system you choose, you’ll want to use an SRS for writing too. I use Anki. You make cards with only the keyword on front. When Anki shows you the word, you write the kanji from memory. On the back of the card you have the kanji. I have it in four fonts, one of which includes stroke order. You also want the story on the back in case you were unable to remember it. You only need to practice one way.
Also, if you haven’t checked out this article from Tofugu on stroke order, I highly recommend you do:
I understand the idea behind postponing learning how to write because you mostly type nowadays. However, I think learning how to write is invaluable. In fact, I would argue that it is better to do immediately, even as a beginner. It helps you remember the kanji better, helps you distinguish them better, and gives you a sense for the whole system that is tough to put into words. You just get more intimate with this beautiful system in a way only learning meanings and readings can’t do. I’ve always thought kanji were cool, but still wondered why Japan doesn’t just get rid of them and switch to a phonetic system like Korea did. Even after only learning to write the small amount I have so far, I no longer think they should do that. There’s something special about this system that you just have to feel through writing.
I hope some of those ideas can be helpful. Let us know how it goes!
I guess it’s pretty well known that Japanese also struggle with remembering kanji (especially if you moved abroad)