The current AA methods are so horrible, FXAA blurs the image to much and TAA blurs the image no matter what(I have spent months on it as well as tsr), tsr looks like a graphics card is throwing up on the screen.
AAA games are starting to look like a smudged up crap show. The only time I can get UE4/5 looking good is with 200% screen percentage combined with fxaa. So I lose tons of frames.
UE needs SMAA!
Where do I start?
The .ush files are usually found in the engine folder for the specific installed engine version you are running. I see no point in arguing with you about the various methods, but have you considered using some other systems such as upscaling?
No upscaling is a different thing, but I totally understand the misunderstanding. Upscaling use to mean that you upscale the resolution as you explained. However, Nvidia, Intel and AMD have created a technology that reduces the screen size from 1920 x 1080 to something like 720 x 1280, but then using a technology to upscale the resolution through some fancy technology. It should exist in Unreal Engine, check: Anti Aliasing and Upscaling in Unreal Engine | Unreal Engine 5.1 Documentation and Screen Percentage with Temporal Upscale in Unreal Engine | Unreal Engine 5.0 Documentation. Hogwarts Legacy is using this type of upscaling, among other games.
SMAA is to expensive unfortunately and the TAA has some pretty cool uses when it comes to shaders.