U have the same set up as mine 2 pc, one at ground floor another at 2nd floor connect using lan cat 6 30m.

Is you Unifi router lan port support 1gbps speed ?

My advice is go for cat 6 cable. You might want to transfer file between those 2 pc with 1 Gbps speed especially moving large files.

You can get those no brand blue colour 30m cat 6 flat cable for less than RM 30 at Shopee.