@slammerkin,
In the US, the libraries have Kindle Book as a checkout option, and the checkout process is actually much smoother than ADE. I don't know what's up with Ohio, but at all the libraries I use, most (but not all) books are available as Kindle Books. It really depends what publisher the book is from. The good news is many books previously available only as Adobe EPUB now have the Kindle option as well.
The woman who had her Kindle account blocked is documented here:
https://www.mobileread.com/forums/sho...d.php?t=194580
As it happened, the books were not wiped remotely, although her account was blocked -- any already-downloaded books were safe. And any vendor can and will do this; it is equally against any ebook vendor's ToS I think.
If you truly wish to be in the EPUB camp, which is totally fine, by the way, do yourself a favor and don't get a Nook. Get a Kobo. There are weeks worth of reading material here and elsewhere as to why, but suffice it to say that the Nook is a dying/dead platform, the hardware is years old and was never all that good, and Kobo has the best customization options aside from having quite decent hardware.
(There you go, a perfectly valid reason to use EPUB, even though I am a staunch member of the Kindle party.

)
But you should know that calibre conversions are just as excellent as the original format, and not epub-centric at all -- except for that all conversions pass through XHTML which basically IS epub.
Then again, AZW3 is basically epub too.
Don't worry about the format, or where you buy the books -- that's what calibre is for. Just worry about the device which is easiest to read on. Some people are afraid of their device vendor controlling/spying on their device, so they don't sign in/connect to WiFi, and there is nothing Amazon/B&N/Kobo can do about it; they sideload all their books through calibre after removing the DRM. They also shop at all ebook vendors trying to find the best price, and usually find it too.
Library books are the one place where that breaks down; while theoretically you can DeDRM them the same, it doesn't really conform to the Fair Use excuse you are using, and is a far shadier thing to do than to strip the books you have
purchased. Even if you plan on doing the right thing and deleting them when the loan expires.