Any tips for must-sees for 10 days in Japan? Also have any hotel suggestions? And is the JR pass really worth it? Any advice is highly appreciated - thank you!

If you're planning on going to multiple different cities, I would say the JR pass is worthwhile. But you will still need to pay for local lines within the city. I think I put about $250 Canadian on a Pasmo card when I arrived and between the JR pass and that card, I was pretty much set for transportation.
As far as must sees:
I loved Nara and the deer. It was probably my favorite part about Japan.
Fushimi Inari Taisha was beautiful and a nice way to spend a morning.
Osaka Aquarium was cool.
Fox Village was fun.
I loved everything about Hiroshima. If you have a JR pass, there's a bus that takes you to all the main tourist locations.
We based all our daytrips out of Tokyo, Osaka, Hiroshima, and Kyoto.

We are still in Tokyo finishing our trip. We purchased the JR 7 day pass in Calgary and also purchase the Skylinner one way airport transfer special which includes a 2 days Tokyo Metro pass for 3,200 yen. These two pass purchase took care of all our transportation in Japan.
Our trip started with 4 nights in Tokyo, then three nights in Kyoto and two nights in Tokyo which we found quite adequate.
In Tokyo, all of the sites and shopping can be reached easily, but prepare for a lot of walking and wear comfortable shoes.
Kyoto has a lot of nice temples and Shrines, and we did day trip to Uji, Inari and Nara from Kyoto.
In Tokyo, we stayed in APA TKP Hotel near Nippori (reachable from airport via Skylinner), it's a new hotel just next to the train station.
In Kyoto, our stay is in a small hotel which is not too bad, but a bit far from the train station, should look for one closer to the station.
For transport , we use Skylinner to Nippori, Metro for friat two days in Tokyo, third day we started using our JR Pass in Tokyo. Then JR to/from Kyoto, Nara, Uji and Inari, and finally JR in Tokyo and JR back to airport using their NEX service.
There are many ways and places you can visit Japan, and this is just our choice based on our preferences.
Good luck and enjoy.

There is a special fare for foreigners- 10000 JPY for any flight in Japan.

If you plan on spending most of your 10 day in one region (such as Kansai), JR pass is not needed. We did Kyoto, Kobe, Nara, Osaka all on local rail day passes. JR stations are far from main attractions in Kansai region. In Tokyo, you can buy the Tokyo Metro Pass (pick from 1 day to 3 day, sold at Narita or Bic Camera) for foreign tourists. All you can ride on Tokyo Metro and Toei Metro. (700 yen for 1 day or 1,500 yen for 3 days). You don't really need a JR pass.
However, if you plan on going long distances in between cities (travelling between Hiroshima and Tokyo), then I'd consider getting the JR pass. JR pass also saves you the headache of figuring out what passes to buy and where to buy.

Also I can recommend bus ticket for Kyoto: buy it at train station in Tourist centre. It will cost you just JPY300

Take a day drip to Miyajima and see the floating torii and take the gondola up and find magnificent views of the area. If you want a challenge, you can hike it up. I loved the Kansai area!

The JR pass is worth it if you plan to move around. It's pricey but all worth for the service you get. Some of those Shinkansen seats are way better than that of an airline.

Kyoto has so many great places and you can buy one day pass at a train station for 500yen/day. So I don't think you'll need JR pass unless you're moving city to city. Miyajima is pretty cool too! You can take a bus from Kyoto to Hiroshima.

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