Looks like the game won't have DLSS/FSR and other TAA-based methods. This is interesting since the Cloud Leopard based version
does feature these, so the team there went through the effort of modifying the engine to support outputting the necessary motion vectors. I wonder if CLE has contacts with Falcom (they are both based in Japan) and if those improvements could be "upstreamed" to Falcom's engine proper.
If there's one feature I think that is sorely lacking in the PC version
(setting aside the lack of TAA or temporal upscaling that you mentioned) is a button binding that will trigger a Steam screenshot. Reason being that SteamInput is disabled by default in this game on DualShock/DualSense controllers (as it's flagged as having native support), and now that I got the trackpad set up to be like the PS4/PS5 equivalent
(I really don't like to use share as a select button, that's just an after-effect from antiquated Xbox 360 controller drivers like DS4Windows), I'd really like to be able to screenshot with the share button from my controller without having to enable SteamInput and essentially losing the ability to have trackpad and share as their own buttons again. I wonder how plausible this binding could be since Steam's API has a hook that allows the developer to trigger a screenshot on their own.
Also, in the starting town area, towards the upper area of it, I'm noticing really strange stuttering issues on my laptop (A 6850M XT/R9 6900HX setup running Linux), but I'm really unsure if this can be replicated in Windows or not. I'll have to test this on my Steam Deck, but outside of that one area, I'm getting an easy 120-140FPS a good chunk of the time at 3440x1440.
Outside of those two issues, this PC version of Ys X is really solid. I'm honestly surprised at the fast release cycle for PH3's ports given the quality.
EDIT: On my Steam Deck running Bazzite, I noticed that the game defaults to Xbox prompts rather than the Steam Deck ones, so there's likely a conflict with SteamInput or there's something up with Bazzite.