Version of Nextcloud and operating system not really relevant.
I use different Nextclouds. The camera from my mobile phone has got 4032 × 3024 pixel.
Nextcloud 1:
https://cloud.server.tld/core/preview?fileId=677793&x=1680&y=1050&a=true
→ preview: 4032 × 3024, e.g. 4 MB
Nextcloud 2:
https://cloud.server.tld/core/preview?fileId=25645949&x=1680&y=1050&a=true
→ preview: 2000 × 1500, e.g. 500 KB to 1 MB
My simple questions:
a.) What is a useful configuration (pixel x pixel)?
b.) What is the default configuration?
c.) Is the default configuration useful?
d.) Where can i set the configuration?
e.) Why i never get 1680x1050 seen in the url (i think that makes no sense)?
Nextcloud 1 is Nextcloud 24, Nextcloud 2 is Nextcloud 23.
But i think the problem does not belong to the release.
The documentation Previews configuration does not really help me.
Personally, i find this question important, as it both delays loading time and can increase the bandwidth needed and thus nextcloud load.