It’s a really good question. I have a fusion, so I don’t know for sure. You should get some on AMZ, in case, then once you' have the iMac open you’ll be able to decide to use them or return them: https://www.amazon.com/Apple-A1311-Bracket-Screws-805-9688/dp/B07GZXRWQH Also, I would recommend an adapter: https://www.amazon.com/gp/product/B01ELR... Here is my SSD now:
USB Install is very straight forward: (1) Follow the instructions here to create your USB with macOS: https://support.apple.com/en-us/HT201372 (2) Install your blank drive. Reboot pressing the R key. Recovery mode will load. The on-screen macOS utility menu will let you access the Disk Utility. Format your drive (APFS/GUID). (3) Then from the main menu select Reinstall macOS.