First time Kobo user, suggestion about Calibre

Hi everyone!
I just got my first kobo, the libra 2!
I wanted to ask a few question:
1) I read that I should convert the book into kepub when I put them on the libra 2. How can I do that? I'm kinda confused about all the plugins in calible:

• Kobo Touch Extended Driver
• KePub Input
• KePub Metadata Reader
• KePub Metadata Writer

Which one should I install? I want both to send books to my Kobo and save them on my PC when I buy them.
2) Since the screen is so good I can finally read manga on it! Should I use CBZ or kepub?
3) There is any way to upload a book on the libra 2 without connecting it to the pc?
4) Do you have any suggestion about other must have plugins on Calibre?

Thanks for the help!