The last ROM I used regularly was AEX. I had a good experience with it. I like basic AOSP, and AOSP plus stock camera is perfect. AEX also has the IR remote app from stock, but that did not work for me. Whoever built AEX did good work, and I used it as a daily driver.
I have also used EMUI 9, 10 and 11. They all worked well, especially 9. I just prefer a clean custom ROM.
The only reason I stopped using AEX was the developers abandoning it. The beta 1 build is almost a year old now, and there is no sign that anyone is working on Huawei ROMs anymore. Why would they? Huawei locked us out, and there aren't many unlocked devices left.
If you don't need all the extra apps and services that Huawei includes in stock, I think AEX is still the best ROM available. And the Mate 20 X is still a great phone.