Cuda is related to Nvidia drivers that you have. Older display drivers use cuda 7.5, 8,.. etc and recent drivers use 9+ (most recent driver use cuda 9.2). You can run miner for cuda 8 although you have cuda 9 (but not vice versa). What is best for you, you'll have to test. Sometimes versions for older cuda work better and faster than versions for newer cuda.
Interesting, thank you. I think I should at least try using the miner for newer cuda, it seems that it would be more appropriate, at least in theory. Thanks a ton, any other feedback welcome of course.