Does it matter which rear mech model I use?

Yes, indeed. Aiming to get a perfectly operational cassette in some drivetrain configurations may cause real headache. Since we've started developing and testing our cassettes there was no clear answer as to whether different brand's components (rear derailleur, shifter etc.) will work perfectly right away with our cassette if you mix-match them or you will need to spend some more time setting up the drivetrain.

What we found out

Various drivetrain components' manufacturers develop their groupsets in such a way to allow them to work perfectly within the same groupset, and it's great until you start mix-matching your drivetrain components. Due to differences in cassette widths, gaps between gears and corresponding shifter/rear derailleur indexing, setting up a perfectly operating drivetrain is a difficult one. Add more variables, such as straight/bent derailleur hanger, worn out shifter cable etc., and bicycle transmission setup may turn into a nightmare. Pictures below show differences in cassette widths depending on the group it's designed for. The difference in fractions of a millimeter is what can make your drivetrain unoperational, especially in 2019 when 11 and 12-speed groupsets exist with very narrow spacing between gears. That is, until you will match components, like cassettes, derailleur pulleys which correspond to the groupset you're using.

How to setup drivetrain right away and avoid any issues

In order to allow the highest performance level possible, we recommend using Garbaruk cassettes according to the "recommended setups" section in the specs, for example: XD-compatible cassette is guaranteed to work seamlessly with SRAM groupset if installed and setup correctly, and Garbaruk Shimano-compatible cassette will work best with Shimano rear derailleurs/shifters.