I’ve looked into those other brands but not recently enough to provide any meaningful comparison. (though I have this feeling that “remarkable is overpriced” is something I’ve heard a lot, but I could be wrong)

I’ve personally owned the Kobo Glo, Glo HD, and Libra 2.

For most of their devices (I can’t speak for current models one way or the other) you can swap out key bits of the software and enhance functionality via various hacks/mods. A lot of that is documented here: https://www.mobileread.com/forums/forumdisplay.php?f=223

You can also open them up and replace a standard SD card to boost storage capacity. (Again, I know this to be true at least through the Libra 2, I do not know about more recent models.)

The thing I got the most use from in the past was being able to swap out the sdcard on my Glo and Glo HD, but some folks really swear by the other various mods. I don’t have any complaint with the default reader software on the Kobo, so haven’t messed with swapping that out.

I have not messed with the SD card on the Libra 2 for two reasons - apparently doing so will mess up the waterproofing, and also because I’ve found 32GB to be sufficient for my purposes.