Graphics or Resolution Issues

[LexRed]

Hey guys, 

I've had this issue where my game runs smoothly on 1080p but since I have a 4k tv, the games looks grainy and weird. Also, this happens on modded arenas, where the default arenas allow me to switch to 1444p which is better. Can you help me with that? would it be a way I can still play on these modded arenas?

I dont really think is my computer performance. I have:

AMD Ryzen 5 3600X 
16GB Ram
Radeon RX 580 8GB

[Cave Waverider]

Many mods are more demanding on your hardware than the default assets, so it's only natural that you see worse performance in modded arenas.

A Radeon RX 580 is rather old and thus a bit weak to run the game at your TV's native 3840x2160 resolution (or even 2560x1440) at a tolerable framerate especially with mods, so scaling will have to do unless you upgrade your video card to something like an AMD Radeon RX 6800 16GB/Nvidia GeForce GTX 1080 Ti 11GB or better.
Keep in mind that upscaling an image will never look as good as rendering the image at a native resolution.

I don't know if AMD drivers for your video card allow for the use of Integer Scaling (I know that drivers for modern Nvidia cards allow for it to be set and some AMD cards do, but I'm unsure if the RX 580 is one of them), which is ideal to scale from 1920x1080 up to 3840x2160 without scaling artifacts since it's twice the horizontal and vertical resolution.
See if the driver software has a setting to enable "Integer Scaling", if it does the image shouldn't be "grainy" as it is with regular scaling.
Keep in mind that it still won't be as crisp as a native 3840x2160 image, but it should be better, especially at a distance. You can try other scaling options as well, if available.

Of course, your TV also needs to allows for the scaling to be handled by the video card without any image "enhancement" techniques from the TV itself (you can try setting the TV to PC or game mode if it has one, disable sharpening and other image enhancement techniques your TV might do), which some TVs or even monitors sadly don't allow.