Actually i never thought about that. U could obviously downsample and just use DLSS on top of it in DLSS type of games.
Also never really knew about LOD's being better at 4k then 1080p, wonder why that is.
I actually should try this out today.
think of distance LODs as proportional. most game engines have a fixed proportion to reduce rendering load of certain stuff. let's say %50
at 1080p, you get 540p-like assets,
at 1440p, you get 720p-like assets
and at 4k, you get actual 1080p like assets
biggest trick TSR/DLSS uses is to not REDUCE model/texture LODs for objects. you see, i've discovered and understood this when I noticted that performance do not scale to the resolution it renders at. At first, I thought it was DLSS overhead (whch is, in fact, a factor). But no, there was something amiss.
In some games, native 1440p rendering versus 4k+dlss quality rendering had a difference of whopping %30-35 FPS. this was huge. this had nothing to do with DLSS overhead. DLSS overhead, at max, causes a %10-15 frame time loss.
Then I understood. DLSS only scales back certain "aspects" to 1440p. not all of them. crucial things such as LODs/assets/post process effects are still rendered as if you're rendering native 4K, hence you claw performance back with DLSS, but retain critical assets at higher resolutions, so that DLSS can be miraculuously good.
here is another RDR 2 comparison. people scoff at DSR stuff and see it just as an alternative AA method. I disagree. the current gen games do not look like at their native resolution anymore. the improvement in this picture cannot be explained by anti aliasing effect alone. there are clearly something different going on here.
see the native 1080p on the left? STUFF is not rendering at native 1080p. TRUST me! look at that undersampling artifacts. its TAA trying to "mold" together low resolution assets. only at 4k+dlss performance combo that game actually looks like it should.
Extra note: this is why some games, RDR 2 in particular, do not benefit greatly from DLSS. because developer chose to not scale back everything. it is good, it gives you some performance and you still get a good image. some games scale everything down, and you see enormous gains. this is why there is not a fixed performance increase for DLSS modes. it all depends on the implementation.