You are probably better off looking through the Kobo sub forums at
https://www.mobileread.com/forums/fo...play.php?f=223 but
1. No you don't need to register (see forum and search for sideloadedmode);
2. try the standard reader and see if you like it - you will get tons of opinions but it is really what you like that matters;
3. Lots of people use the kwmobile sleep covers which are cheaper than the official Kobo one's and are reasonable quality.