I think like my colleagues here, the Amiga catalog is mostly PAL, with some minor exceptions.
I already reported this problem of speed and stretched images in a previous version of MegaAGS, "Lemmings 2" had been the example in that message, where this effect is very clearly seen.
This is why I prefer to set the system to PAL and then we´ll be free to look for specific fixes to the few NTSC minorities, I think it´s a better starting point than doing it the other way around.
My favorite solution to do this is to force PAL, but the problem is that rebooting removes the option, and what we want is to simply set all games to PAL permanently. That´s why I´d found a fix for this that works the same for this version of MegaAGS, and I´m sharing it here in case someone else wants to use it:
It´s just copying the whdlvmode once PAL is selected in the image, and it remains permanent.
So first, we select the PAL option in the MegaAGS image with the menu option for this purpose, then we press ESC to exit to the workbench, we open Diropus, go to this path "RAM:ENV/ "and we copy the file "whdlmode" located there to "DH0:PREFS/ ENV-ARCHIVE/".
And after that our PAL compilation is safe from reboots.
Cheers!