one of the main problems with ue5 is that the packaged effects and tools aren't actually good for performance. nanite sucks, lumen sucks and the non-raytraced methods have stagnated in the engine because of it, TSR, extreme use of dithering, etc. you would have to rip all of that out and replace it with plugins or integrate open source methods (amd or intel AO solutions, dlss/xess/fsr, fsr framegen(it's device agnostic), temporal smaa to get away from the bad ue5 TAA, list goes on. the blueprint system and editor are the nicest things it actually offers, the rest of the features have been an observible disaster for the gaming industry.