@dankcushions Thanks for your very elaborate answer! I naïvely assumed that at least the region detection was straightforward (e.g. some flag in the internal ROM header), but after some reading it seems that the region was indeed only "coded" physically by incompatible cartridge sizes. Some bytes of code and data saved I guess.

I'll just manually set the 50Hz rate. I'm definitely grateful that it can be done conveniently in a few seconds!

Unless you're connecting your Pi using a composite cable to your TV (which seems unlikely, since that won't do 1080), NTSC/PAL is not an issue for TV's video resolution.
Use raspi-config to choose your desired video resolution globally or modify your /boot/config.txt according to the Raspbery Pi video doc.

It is very noticeable on certain games. Try WWF No Mercy on n64, it's night and day the PAL Vs NTSC versions.