How can I connect a Samsung Portable SSD (USB C/3.1)to a Mac mini with Thunderbolt 2 and USB 3.0 (Late 2014 Mac Mini)

I have a late 2014 Mac Mini (3Ghz Core i7, 16GB RAM DDR3, 1TB Fusion Drive) I want to use the Samsung SSD as a bootdisk for Beta testing Mojave. I have connected the SSD to the Mini using the Samsung USB to USB C cable (provided). Seems to work OK with 10.13.6 and Mojave Beta but is there a better solution? The mini has two Thunderbolt2 ports which seem to be incompatible with anything. Is there a USB C (3.1) to Thunderbolt 2? Should be faster throughput? Is the USB to USB 3.1 connection OK or will it harm my Mini? I believe the Mini still is the best solution for me. Is Apple planning a new mini with Thunderbolt 3?