I know, it depends on the type of use. If I use the IPad with a keyboard as a laptop replacement, create Word documents, make a few Power Points, etc, download a few movies on Netflix and download a few games on the App Store: Then 64 GB or should I rather 128 GB orientate?
You should not save on the memory.
I also had the choice between a 64 GB and a 256 GB iPad Pro and opted for the larger memory, because if you do not miss it if you really need it and upgrade it is not nunmal!
Therefore rather spend 100 euro more and buy you the larger memory.
For your called usage behavior, I would rather advise you to a 128GB model, since the memory after downloading some games, movies, etc. Can be faster full than you would like.