My last Kobo was bought 4 years ago so it may be different but it was very slow compared to a Kindle bought at the same time. Searching for books took a very long time. Looking through your library was click next, wait 10s, click next, wait 10s.
Once you were in a book it was perfect.
I only use Calibre to push books on to the device so I can’t speak to their store. With that modifier - Kindle can’t do that well at all so it’s a non-starter.