If you are shooting stills, then any card is going to be plenty fast. Of the two brands I trust, SanDisk and ProGrade, only SanDisk offers a 64GB card, but a ProGrade 128 isn't much more expensive.
At first, ProGrade was offering 120 GB cards that were a little slower and cheaper. I ordered some, but it was the 128 GB version that actually shipped. I consider 128 GB a pretty good compromise for stills -- plenty of storage but not ridiculously expensive.
Video is another matter and I believe elsewhere on this site there is a link to a Canon reference sheet that identifies cards for video. I seem to recall that ProGrade and SanDisk have higher level cards that Canon said were best for 8K. I'm sure someone will share that link.