You'll also be able to play the original European PAL release of some titles.
Nintendo UK has confirmed that the library of N64 titles coming to its Switch Online service will run at 60Hz. This will have likely put the fears of many European fans to rest, as it was widely assumed that these older titles would be the original 50Hz PAL versions. If you are looking to play the original PAL versions though, Nintendo has confirmed that this will be possible for some select titles and that there will be some different language options.
No word has been released yet on when these titles will be hitting the service and how much the new Nintendo Switch Online Expansion Pass will cost, but it shouldn't be too much longer now as we are just roughly a fortnight away from the end of October.