You probably don’t need both MNN and Genki. Honestly, they seem to be roughly equivalent. I’ve heard that MNN takes you a little further, but the difference isn’t much, because both of them will get you essentially to the beginning intermediate stage. If MNN spoke to you more, then I’d just try that one, and if you end up frustrated, you could sell it and try Genki instead. Genki and MNN both have their own benefits and drawbacks, and different books work for different people.
A Dictionary of Basic Japanese Grammar is great, though, and you can refer to it as needed, so I can recommend picking that one up regardless of whatever path you end up choosing for grammar!
As far as kanji goes, I’d try a few levels of WK and see how that works out for you before purchasing any other resources. If WK proves to be an effective tool for you, you probably won’t need additional resources for learning how to read kanji at least. You would need to find another way to learn how to write them, though. One user here has helpfully prepared kanji writing sheets that have all of the kanji for each level. There are also loads of scripts you can install that add information like stroke order and semantic-phonetic composition to the kanji pages in WK. WK can get pretty time-intensive, so you probably won’t have a lot of energy to do a whole lot of kanji study outside of your SRS reviews and grammar/vocab study. I’ve been learning to write kanji as I learn them, but most people consider that to be optional at this stage, if your primary goal as a beginner is reading comprehension.
I would also caution you against doing too much, especially as a beginner. That’s a very good way to burn yourself out! I’d recommend doing the first three levels of WK before buying anything. If that goes well for you, you could buy a subscription to WK, then decide on a path for grammar. Starting MNN around level 5 worked out pretty well for me, because by then, I’d gotten good enough at reading hiragana through WK that that part of MNN wasn’t a problem, and I understood enough grammar basics from Japanese Ammo with Misa that adjusting to that wasn’t an issue, either, and kanji no longer scared me thanks to WK.
It’s also a very good idea to develop a daily habit with WK so that you have a regular, predictable daily workload. I do 10-13 lessons daily, and do my reviews three times a day so that I can hit the first three review intervals for the new items. I also use a program called Kaniwani which uses the same SRS as WK, but goes from English to Japanese (another program that can do this is Kamesame). It’s useful to get practice on the other direction, but it also adds a lot of studying time to the WK workload, which you have to be prepared for!
If you manage to do WK consistently for at least 5 levels, you’ll start to get an idea of what speed works for you, and how much time you’ll need to put into it daily to keep up. At that point, I’d recommend adding one other resource, be that MNN or Genki or Tae Kim or Bunpro or any other tool. If you manage to work that other resource into your daily schedule and still have time for another thing, you can consider adding another, but all of this stuff adds up a lot, especially multiple SRS.
I don’t think I’d recommend doing more than two SRS at once, so I’d caution you with Bunpro if you plan on doing WK and Anki (or Kitsun) at the same time. I’m technically doing three, but Kaniwani is just reinforcing the items I’m learning through WK, and my daily Anki review load is very light because it’s tied to my pace through the textbook (I’m working through MNN at a rate of about two weeks a lesson). If this ever gets to be too much for me, my plan is to slow down on WK lessons (which would also slow down Kaniwani).
The knowledge you’re getting from flashcards tends to stick better if you apply it fairly soon after, anyway. SRS is very good at putting a high volume of information in your brain very efficiently, but we learn language by actually using it. That’s why I ended up going with the MNN + WK combo, because the textbook gives me loads of opportunities to apply the vocab and the grammar that I’m learning together instead of trying to learn a bunch of different aspects of the language in isolation. It’s why many people on this forum have found success with primarily learning through immersion, because when reading native materials, you’ll also be learning vocab and grammar together with context, and that will benefit you more than studying flashcards in a vacuum. The language in a textbook is more artificial than what you’d find in manga or anime, but textbooks can give you a good foundation of knowledge that you can then build off of by seeking out native materials once you can read basic Japanese.
I think it’s very easy to collect way too many tools when trying to figure out how to study Japanese, and trying to do too many things at once can burn you out or cause you to give up because you get paralyzed by indecision. There are loads of options, and some work better for some people than others. I wouldn’t listen to anyone who claims that any one method is the single most efficient or effective method, because even just on this forum, there are people who have reached a high level of proficiency in the language with a variety of different methods. I think the most popular recommendations here tend to be 1) going with a textbook, or 2) downloading a flashcard deck of core vocab words and combining that with a grammar SRS, or 3) forgoing textbooks and core vocab decks entirely and trying to engage with native materials as soon as possible either by prelearning some specific vocab and grammar before attempting to read, or by looking stuff up as you go. You’ll find people in all three camps who feel very passionately about their choice, and believe it to be the right choice for them. The best choice for someone else may or may not be the best choice for you!
All of that said, I am extremely far from being an expert, haha! I only have a few months of experience actively studying the language myself, but I’ve read a lot of discussions on this forum and elsewhere, and my main takeaway from everything that I’ve read is that these are questions that have more than one answer. I wouldn’t take any one opinion (including any of mine haha) as absolute gospel truth about the best way to learn. Most of us are speaking purely from our own experiences, and those tend to differ a whole lot.