[popcornmix]

I see that you still set default video players in advancedsettings.xml, even though dvdplayer is "used" for both now.
Is this necessary?

Where is this? I believe not specifying the player will result in dvdplayer being used which is correct.

And I am also wondering about the imageres and fanartres (advancedsettings.xml).
What is default when nothing is set in advancedsettings.xml?

imageres and fanartres both default to 1080. That is too high (especially the imageres, as you may have many posters on screen at once in the poster wall views and that will just exhaust gpu memory).

Also, how do you distinguish which video player being used (in log and on screen info)?

Bring up codec info:
omx-h264 means omxplayer
mmal-h264 means dvdplayer with hardware acceleration
ff-h264 means dvdplayer withouth acceleration

One more; Any reason to change anything regarding readbufferfactor and cachemembuffersize or should I leave that at default?

cachemembuffersize should be unset. You then get the automatic behaviour of 20M on 512M Pi and 2M on 256M Pi.
I think readbufferfactor should be higher on the Pi. Set it to 4.