JR East: Online Seat Reservation for Joyful Trains with nationwide JR Pass?

I used Google and the reddit search function, but couldn’t find a definite answer to this question. So maybe someone can give me a quick answer.

I’m thinking about buying either the nation-wide JR Pass or the JR East pass for an upcoming journey. As a train enthusiast, I’d like to include at least one or two of those Joyful trains.

I’ve discovered that it should be possible to perform such a reservation online via JR East. However, the website only lists following options when selecting “Passes purchased elsewhere”:

* JR EAST PASS (Tohoku area)
* JR EAST PASS (Nagano, Niigata area)
* JR TOKYO Wide Pass
* JR Tohoku-South Hokkaido Rail Pass
* JR East-South Hokkaido Rail Pass
* Hokuriku Arch Pass
* N’EX TOKYO Round Trip Ticket
* HOKKAIDO RAIL PASS

So:
1) Can I just select one of those options and show up with the JR Rail Pass instead (presumably not)
2) Is there some other way to reserve a seat on non-Shinkansen trains with the nationwide Rail Pass?
3) Do I need to worry about seat reservations for “joyful trains” during mid-april travel?

That’s the website I was looking at:

[https://www.jreast.co.jp/multi/de/pass/eastpass\_t.html](https://www.jreast.co.jp/multi/de/pass/eastpass_t.html)