I updated to EMUI 12 after doing a factory reset.
Then, I disabled a few of the apps / services that I normally do not use such as chrome, photos, google search etc. etc.
Anything that i disabled I also did in other phones that I own because I always found out these would slow things down a lot. That is in my hands.
I also use blokada with an extensive host file which blocks a lot of tracking, background connections etc.
I keep automatic sync off.
I am not interested in following instagram, tiktok etc. I do not play PUBG and similar.
I have to say that the phone is super snappy, i see no lags and no problems with more than one app open.
Regarding picture quality, initially they seemed a bit mmmmmmh when looked at on the display of the phone. Then I forced high resolution (the automatic one does nothing in my eyes) and they looked better.
The real test would be to look at them at 1:1 resolution on an external display. This should also be done for the high-res pictures. Normally these high-res tweaks do not look any different from normal on the phone screen.
I haven't done that yet.
However, it seems to me that post-processing is different and that pictures now are softened rather than sharpened like on EMUI 8.
My personal opinion is that when a new phone comes out, Huawei optimizes a lot the rom and the camera app for that phone for the wow effect for the release of a new product (e.g. reviews).
As time goes by and new models come out, the older phones receive sort of "generic" software that does not really leverage on the specific hardware of each model.