Pass or not? JRpass or regional?

Hello, here below the idea of my trip (beginning of September).
I cannot understand if using a pass (or a combination) and which one.
If not, how can I organize buying in advance the main transfers to simplify the trip when I'm there?
And do I loose some discounts or advantages without a pass? I refer to tickets for touristic sites or metro or bus etc.

Thank you for any advice both on transports and itinerary.
Day 1 - Arrival to Tokyo (1pm)
Day 2 - Tokyo
Day 3 – Tokyo
Day 4 - Fuji (day trip to 5 lakes)
Day 5 – Tokyo + transfer Hiroshima (6pm)
Day 6 – Hiroshima and Miyajima + transfer Osaka
Day 7 – Nara from/to Osaka
Day 8 – Transfer to Koyasan and night
Day 9 – Transfer to Kyoto (bus Osaka+train)
Day 10 – Kyoto
Day 11- Kyoto
Day 12 – Kyoto
Day 13 – Transfer to Kanazawa in the morning + visit town and night
Day 14 – Shirakawago + Takayama and night (by car or bus)
Day 15 – back to Kanazawa and transfer to Tokyo (or straight to Tokyo from Takayama)
Day 16 – Tokyo in the morning and flight back