Overnight train Osaka-Tokyo with JR (extra fee?)

Hi! I check 2 different webs and now I'm a bit confused with overnight trains, I hope you can help me.

I'd like to get the overnight train from Osaka to Tokyo.
Do I have to pay an extra fee having the JR pass?
Are they only with seats or is it possible to get them with bed?

I'm also not sure if to get 21 or 14 days JR pass, as I've seen in so many blogs that they recommend less days than the ones you are gonna be there but as I'm gonna be there for 19 days, I'm not too sure what is the best to do. This is my itinerary:

1- Osaka
2- Tokyo
3- Tokyo
4- Hakone
5- Kamakura - Yokohama
6- Tokyo
7- Tokyo
8- Takayama
9- Takayama
10- Shirakawa-go - Kanazawa
11- Kanazawa
12- Kyoto
13- Kobe
14- Hiroshima
15- Miyajima
16- Kyoto
17- Kyoto
18- Nara
19- Osaka

Thanks for your advice and have a nice day! :)