In principle CD-i titles are region-free so the European CD-i titles (PAL) are exactly the same as the USA (NTSC) CD-i titles. On the back of the titles you'll see "Philips Interactive Media of America" indicating it is a USA title. Their address is on all back covers. European titles are all made in Germany (at least most of them, some are printed in UK or The Netherlands). You won't run into any issues like 50/60hz differences.
"Finally, the CDi has no copy protection right? So I can just burn an ISO to a disc and it’ll work? No special things I need to be aware of?"
CD-i titles have no copy protection, that's correct. You can find various ISO files of CD-i titles on websites like Gametronik. The only thing to keep in mind is when you want to create an ISO out of original CD-i discs are CD-i Ready discs. Those are more difficult to rip.
CD-i member Arethius RGC about this: "It is funny I never had issue with the music of NTSC game on PAL console. I was told that music was always at 60hz or at least the music speed was always the same.
On cd-i there is no region lock it seems that only the screen format will change."
Jorg Kennis about this: "A CD-i consumer player is usually suitable for a dedicated TV standard, such as PAL or NTSC. Some professional players have a switch at the backpanel to select the appropriate TV standard. A CD-i disc is TV-standard independent: any CD-i disc can be played on any CD-i player where-ever in the world. But due to the characteristics of both TV systems, special care has to be taken into account when designing a CD-i title. An NTSC-display usually displays slightly less lines, with slightly less pixels on each line. Usually the NTSC display is 720x480, compared to 768x560 for PAL. When a full resolution image is displayed on an NTSC-display, the most outersized pixels will drop out of the picture. When an NTSC picture is displayed on a PAL screen, very small black bars are shown at the bottom and top of the screen (these bars are really small and should not be compared to the black bars of a letterboxed movie). For this, the 'safety area' is defined, the size of an image that is expected to be correctly displayed on all TV-sets. This safety area is 640x420, no 'critical' information such as menu buttons should be displayed outside this area. The same limitations with respect to the safety area apply today to DVD-Video titles that are to be distributed world-wide."
[Thanks, Aydan Watkins]
[Thanks, Aydan Watkins]