The cards are all about the same 1700 read and 1200 write. The slowest card is also the smallest capacity with 64GB storage and 800 MB/s write. I would buy on capacity. That slow card isn't going to store a lot of footage so by default you'll get a faster card.
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.