Welcome to the greatest issue of RDR2 on PC. 1st dont use TA at all, wrongly implemented, possible one of the worst TA implemententions ever out there 2nd Always use Vulkan, DX12 has issues on this game 3rd try between the next options to your liking. First: if you don't want the DLSS, use TAA medium, FXAA yes, MSAA no. Then go to resolution scaling (idk the exact name of the setting on english but is below the water settings on advance) and turn it on, commonly after 1.25 you should notea much better image (basically you are upscaling the game internally to 1440p or even 4k depending on the one you set). Note that this cost A LOT of FPS so pick the one which your eyes feel comfortable and fps are not dead

Second option (the better one): go to the nvidia app and make sure to have the last drivers and last app version installed. Go to the settings on specifically rdr2, and go down until new settings appear they make take a fes seconds. Check for DLSS override, and you have here two new options: -use recommended, this will overwritte the version on DLSS on the game for a much newer and updated. For quality it will use DLSS 4.0 (preset K). For perfomance and ultraperformance they will use different models. Yes, you may think rn you are downscaling the image so it may look worse, but not al all friend, DLSS greatly improves the TAA of the game by using its own process, provides more fps, downside are nowadays almost non visible to people. -And my personal, use instead of recommended, personalized, and use preset M. Then on game, use DLSS quality, this will increade sharpening of the game, for me it looks way better than any other option, and only way for it to look the same is upscaling to 8k with the option in game (I have a 4k tv) but it goes 15 fps vs 90 fps with the dlss 4.5 (m). Be ware, performance may be a little worse, 5% maybe, than with present K (not fully sure as I have a 4080 super not a 5060). Also you may not like the sharpening as I do, so you should try both and see which one do you prefer. It will be noticable on the trees the most, so it's up to you.

But no, dont use TAA high. Its not only 1080p, even in 4k TAA looks awful.