Video performance with RX580

Hi guys

After some (ridiculous) issues getting it to work, I finally got my old rig to work with an RX580 and thus updated to Mojave.

Thing is I find the video quality to be... Sub par. Pixels are fuzzy, quality is blurry, and I see a lot of artifacring on transparency effects.

I also upgraded my monitor to a BenQ 4k display so it may be either or a combination but I don't really have a base of comparison so I'd like some pointers to start investigating.

I'll try to hook up one of my MBP to both HDMI and DP to the monitor and see, but I'm not even sure if I should expect a difference or not.

Any ideas?