This is not for the BTT tft50!, This is for the aliexpress $20 Screen. Its 5in and its DSI. If you need a longer cable make sure you get one that the ends are the same on each side! the btt tft50 has ends that are the opposite. Will need heat nut inserts for the main base and 6-8 mm m3 screws?

i would use the bigger one, they cut the PCB and its not the same from batch to batch

Link for Screen!

https://s.click.aliexpress.com/e/_msbSI71