I'm planning on completing to the following journeys using a JR pass and was thinking of buying a green car pass however I'm not sure how many of my journeys will have trains with green cars. If someone would let me know I'd really appreciate it. Also regarding green cars, do I still have to reserve seats in advance or is it really not necessary?
Narita to Tokyo
Tokyo to Takayama
Takayama to Kyoto
Kyoto to Nara
Kyoto to Hiroshima
Hiroshima to Tokyo
Tokyo to Nikko