I won’t charge them faster than 1A. I would always discharge test at 1A. This way you get the most capcity out of them. It won’t be the real capacity you’ll get in the field since you are going to run them at their limits all the time, but for comparing the individual cells I’d go with 1A.
I stopped using the imax for capacity testing since it can only do 1 cell at a time. one of those $30 opus chargers can discharge test 4 at a time. also I think the imax is limited to 1A discharge testing while the opus can either do 4 at 1A or 2 at 2A.
As for the BMS… I don’t use one since my setup will never draw more than the battery can provide. I only use one of those $15 ones off ebay for balance charging the pack.
For you setup I would highly recommend using a BMS though… one that limits current drawn from the battery to no more than 40A (get a fuse, too). don’t know wich one is good though… I would just try one of those 10S 40A ebay ones.