If your library doesn't support Overdrive, then I think getting books on Kobo might be more difficult. Though I imagine still easier than a Kindle, which is far more locked down than Kobo. I don't know a workaround though - Reddit might be more useful.
I only really know Kindle as that's the ecosystem I'm in. With a Kindle, you're pretty locked in when you're there if you want to keep your library of books. All kindles have the same screen resolution now so the differences between the models are:
Basic
Touchscreen only
Smallest screen
Inbuilt lighting, but no option to change the colour temperature
Not waterproof
Paperwhite Basic
Touchscreen only
Larger screen than basic
Waterproof
Lighting with option change between warm and cool light
Paperwhite Signature Edition
Same as basic Paperwhite except
Wireless charging support (dock sold separately)
Auto adjusting light
Bigger storage than basic Paperwhite - though this is only likely to be an issue with audio books or graphic novels. My 11 year old Kindle is only 2GB and I've had no issues with that, so 8GB will be fine for the majority of people
Oasis
Slightly larger screen than Paperwhite
Page turn buttons
Wifi and cellular connectivity
Auto adjusting light
However, it's the only model still with micro USB charging (all others are USB-C) and it hasn't had a refresh in years
Scribe
Huge screen
Can use a stylus to write notes
Auto adjusting light
Not waterproof