In which case either card is a good choice from a performance perspective, just not a price perspective. As for the RM1000e I don’t know enough about the quality of that model, probably a good choice but best let one of the PSU experts confirm. A high quality 1000w would do the job.
I have a 3080 for 1440p 240Hz it does the job but it’s nowhere near overpowered. Had the 4080 been more reasonably priced I would have upgraded but at its current price the performance gain is not worth the cost. If I am spending that much I want a bigger boost in performance so will probably end up waiting for 5000 series unless a great deal on a 4080 comes up this year. As for the 4090 while I could afford it I don’t want to, it’s just too much for gaming for something that will be outperformed by next gen cards for much less money and will likely loose £1k value by that time, it just seems like a bad deal.