I pixel peeped RC Rift Apart at 1440p and I'd rate the upscaling solutions as follows:
1. DLSS
2. XeSS
3. TIE -> FSR3(more artifacts) and IGTI(blurry)
4. FSR2
DLSS 'Performance' has better image quality than FSR3 or IGTI 'Quality' modes. The ideal use of FSR3.1 for Nvidia users on older cards who are locked out of DLSS 3 FG to pair DLSS with FSR3.1 FG. Obviously it's giving AMD users a little bump in image quality, too.
For Steam Deck it doesn't really help in R&C Rift Apart because the Deck doesn't have the headroom to hit a stable 60fps frame gen target. Same for some of the Lossless Scaling testing I've been doing. Some games can, but more demanding games can't. Something like a 6800U or 7840U might be the minimum hardware to pull it off assuming it's mostly GPU-bound.
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Just played the opening segment of Rift Apart. FSR3 FG actually looks really clean in combination with DLSS 'Quality'. Seems to be more performant than DLSS FG. Maybe like 10-15% rough estimate. I'm on 4060Ti 16GB+5800x3D+165Hz monitor, and put settings to 1440p(DLSS 'Quality'), Medium preset with 16xAF, RT Reflection High+10 render distance. Playing with frame rate commonly hitting 165Hz looks really fucking amazing.