I'll be doing a solo trip to Nagoya for 12 days from late October to early November. I seek your advice if the following itinerary is doable, which transport passes I should get and if I should bring along my luggage from place to place.Basically your plan is doable. You can bring your luggage throughout your trip if you minimize your luggage (clothes for three days in a backpack, maybe less than 7 kg).
You may better consider Tateyama Kurobe Alpine Kippu Hida Course, valid for 8 days, Nagoya-Toyama-Shinano Omachi-Nagoya, 21180 yen.
https://railway.jr-central.co.jp/tickets/otoku_tateyamakurobe/Unfortunately there is no English page for this kippu (ticket). But this is the only pass the validity of which is as long as 8 days. Note that this ticket is not sold in Centrair airport station which is operated by Meitetsu, a non-JR company. So you must buy ticket for Centrair to Nagoya (less than 1000 yen) or use IC card.
Day 1: Nagoya > Takayama
When you buy Tateyama Kurobe Alpine Kippu Hida Course at JR Nagoya stationfs ticket office you should reserve reserved seat for Hida express.
Day 2: Takayama > Shinhotaka Ropeway > Hirayu Onsen (stay over at one of the Ryokan with in-room private onsen)
Kamikochi/Okuhida Marugoto Value Ticket
Covers Hirayu onsen, Shinhotaka cable car and Kamikochi.
https://www.nouhibus.co.jp/marugoto_value_ticket_en/Since you are travelling solo it might be difficult to find room for your preferences (in-room private onsen that is).
2 day vershion 9600 yen if you donft stay in Kamikochi, 3 day version 10400 yen if you stay in Kamikochi.
Day 3: Hirayu Onsen > Kamikochi > Takayama
I recommend to stay one night in Kamikochi. Nishiitoya mountain lodge is my favorite.
Day 4: Takayama < > Day trip to Shirakawago
You can do Shirakawago on your way to Kanazawa. So Kamikochi to Takayama and stroll Takayama on day 4.
Day 5: Takayama > Kanazawa
Takayama to Shirakawago to Kanazawa by bus. There are coin lockers in Shirakawago bus terminal. You donft use Takayama to Toyama section of the Tateyama Kurobe Alpine Kippu Hida Course.
Day 6: Kanazawa > Toyama
You must pay Kanazawa to Toyama section separately. 59 min by non-JR trains, 1290 yen or 23 min by Shinkansen non reserved seat 2860 yen.
Day 7: Toyama > Tateyama Kurobe Alpine Route > Matsumoto
Murodo has coin locker. In the worst case you may encounter snow storm.
Day 8: Matsumoto > Nagoya
Reserve Limited Express train reserved seat at the ticket office in Matsumoto station usein your Tateyama Kurobe Alpine Kippu Hida Course.
Day 9 to 12 (morning): Nagoya (include Nabana no Sato, Legoland, Ghibli Park and/or Nagoya Mitsui Outlet Park)
You can wash your clothes in most of your accommodations. Of course most convenient is in-room washing machine but this type of rooms are in general more expensive.