I am brand new to Wanikani too, but not to spaced repetition. I have been using it for about fifteen years, maybe longer.
Probably your question has been answered in some other threads, as others have suggested, but if you don’t mind I will humbly share some of my personal experience.
Extra studying absolutely does not interfere with spaced repetition. For one thing, your spacing will adjust to how well you remember things … so, if you know things already, or you are remembering them very well due to extra studying, they will zing off into the future with months between repetitions.
The theory of spaced repetition tells us that if we want to remember the absolutely maximum amount of stuff in the absolutely minimum amount of study time we should adhere exactly to the schedule. But life and even learning theory tell us otherwise. I notice already that there are a lot of serious SRS people here at Wanikani. If they are anything like me, they create tons of cards while they do their reviews. The act of creativity is largely missing from a strict adherence to the learning schedule. Yet it is an essential part of study. For me, I rely on physical exercise for learning as well, which is obviously difficult while in front of a screen. So I create audio stuff that I can do while swimming or whatever. I also enjoy drawing kanji with a brush, which is missing from these tutorials, but is a extra reinforcement for those who enjoy it.
None of this contradicts SRS theory or its implementation here.
Another great thing about reviewing and learning in other ways is the positive reinforcement that you get when you recognize something that you have learned in lessons. For me, I am starting to read signs pictured in passing on the street on NHK, and also starting to pick up bits of conversation. This excites me inordinately. I start raving about how I am really learning Japanese, to whoever will listen (generally my dogs and cats and spouse) . I am sure that this is tremendously effective, in any theory of learning.
When I started with SRS, Supermemo was all that was out there. I still keep a version of Supermemo on my computer, for old times sake. It was so hard to learn, although the hardcore Supermemo people would deny that. However, I think that it would be worth your time to go to the supermemo website and read about SRS.
Here are the supermemo rules for formulating knowledge.
As a person who is a long time believer in and pied piper of spaced repetition, I would say that it may be worth your time to download Anki (a popular, open source, well maintained SRS system) and spend some time learning it. But it really is a whole project into itself.
Best of luck to you.