Using a Samsung T7 2TB SSD drive with Apple Macbook Pro M1 2021 - what format should I be using?

My old Macbook Pro Retina (mid 2012) ran fine with T7 drives but I have had real problems with my new 2021 M1 Macbook Pro - very, very slow performance. I gather that the formatting of the SSD drives as supplied is not really compatible with the Macbook and that I need to reformat the discs. Apple seems to offer two Apple options in the Disc Utility programme one off which is identified as case sensitive. What does case sensitive mean and which should I use? I want to use the drives for storing pictures and for Time Machine backups. Thanks