Itinerary for central Japan in Apr 19

I have planned a 9 days trip in central japan, basically to do the nakasendo trail. The trail will take 4 days starting from Nagoya and ends at Narai. I have questions about the Tateyama Kurobe Alpine Route since I will be there in mid Apr.

My initial itinerary for my trip

Arrive Nagoya on 12 Apr and spend a night before starting the nakasendo trail the next day.

13 Apr - end the walk at Tsumago and will take public transport to Forespakiso Atera Ryokan
14 Apr and 15 Apr 19 - Nakasendo trail and spend 2 nights at Urara Tsutaya (Kiso-Fukushima)
16 Apr 19 - take a train to Matsumoto and hope to do the Tetayama Alpine Route
17 to 19 Apr - Wish to cover Shiragawa-go, hiragu onsen and Kamichochi
19 Apr - return to Nagoya
20 Apr - flight home

My base from 16 to 18 Apr has not been planned as I am still trying to figure the transport mode for travelling these places. I also understand Kamichochi will open on 17 Apr 19.

Appreciate you could advise, based on the above places of interest, what is the best option in terms of convenience and most economical. We are 4 adults travelling together.

1) purchase Tateyama Kurobe Option Ticket which is one way, for the apline route and the rest of journey using the rental car
2) purchase Alpine-Takayama-Matsumoto Area Tourist Pass for 5 days ( this route is inconvenient as need to arrange for luggage transfer )

The nakasendo trail is confirmed but the rest of itinerary is feasible and adjustable. I will also need advice the scenery and weather during my period of travel.. or any places i miss out from my itinerary. Would appreciate comments and advice. Thank you.

You need to check the dates for the Alpine Route. For example, it opens on the 15th of April this year.
https://www.alpen-route.com/en/

And the first 2 weeks are massively busy. So you don't want travel from afar and attempt to cross the route from mid morning. So unless you start your day in Nagano, Matsumoto or Toyama. Then I wouldn't attempt it.