What FPS will I get in DOOM Eternal at 1440p?

At 1440p Ultra native, expect around 180 FPS. With DLSS Quality you can push higher.

Does GeForce RTX 5090 VENTUS 3X OC support DLSS or FSR in DOOM Eternal?

Yes — DOOM Eternal supports dlss2.

Yes — the GeForce RTX 5090 VENTUS 3X OC runs DOOM Eternal at approximately 240 FPS at 1080p Ultra (native, no upscaling).

✓Yes — Excellent

Expected: 240 FPS @ 1080p Ultra (native). This GeForce RTX 5090 VENTUS 3X OC is currently $3929.05 at Amazon ↗