u/Efficient-Key-6640

I have a 1TB (Lexar NM790) and a 2TB (Kingston FURY Renegade) SSD and Gigabyte B650 Eagle AX motherboard. Slot 1 is a Gen 5 x4 ( or Gen 4 x4), Slot 2 is Gen 4 x2 (around 3500 MB/s speed). Both via CPU. Slot 3 is Gen 4 x4 via chipset. Which slots should I use and which drive should I use for the OS? I only game, browse and watch media on the PC.