I am applying for graduate schools in Math and I was wondering if it is okay to talk about what courses I plan on taking this Fall and next Spring before the beginning of Fall 2022. Should I talk about this in my CV or SOP?
This is not something for the CV, which lists your past accomplishments of various kinds.
It is more the stuff for the SoP, but it might be a bit too detailed - especially listing specific courses. But you should at least talk about which major subfield(s) you are most interested in. In my case it was both Analysis and Topology. But it was a bit more specific: Real Analysis and Classical Topology. (Note that this was long ago).
And don't forget, in the SoP, to also write about longer term plans. Making it a bit general gives you options, but not so general that you seem to lack direction.
But, since you mean courses you will take before you actually start the degree program, then you could name a course or two in support of the goals you list. "To support my goal of studying Topology in the future, I'm taking a course, now, before, the program begins." (Hopefully you can phrase that better.) But the bulk of the SoP should be about your plans for what you will focus on in grad school and what you intend to do with the resulting degree.
If a course has been completed, then it might be appropriate to list in the CV. Make the CV about the past and the SoP about the future.
And note that this will count for little, since it is still unknown how you will do in those courses. It shows some dedication to your studies and seriousness of purpose, but that is all.