Help for hotel in Venice. Wayyy overthinking!

Using Booking.com search for the dates you are interested in. Filter the amenities you are looking for.
There are 6 districts in the historical center, called “sestieri” (1 sestiere = 1 sixth of the city).
https://en.wikipedia.org/wiki/Venice#Sestieri

San Marco, is the most central but also the most crowded and most expensive.
All others are still very good because the historical center is not that big and very walkable.
I have always stayed in Dorsoduro or Cannaregio.

In the article below there is a map that shows the flow of foot traffic in Venice. The red streets are crowded the most, the yellow less so. The green streets have low foot traffic. Generally as you move away from the Grand Canal there are fewer tourists.

https://www.wired.it/attualita/ambiente/2017/07/14/venezia-accesso-piazza-san-marco/

$500 a night is not low budget so you should be able to find nice places. Booking.com allows you to filter the facilities with AC (although at such high price all hotels will have AC). Not sure if you can select rooms with a bath tub rather than a shower. You should be able to see the furniture from the photos displayed for the rooms of each hotel.

Hotel Ala is our go to in Venice
Lots of fans here as well

https://www.hotelala.it/

It is right near the SGiglio vap stop so no bridges or steps to access, in a quiet campo. Fantastic bkft, lovely staff
You don’t need a private dock

We love Hotel Ai More D'Oriente, in the quiet and charming Cannaregio area. No crowds yet a great Venetian vibe. For that budget, you could have a suite- book directly for the best price. The hotel has a dock, so you could use the water taxi. The train station is a 15 min walk, and the vaporetto stop on the Grand Canal about an 8 minute walk.
As I remember, there were tubs, but I don't know about all rooms.
Enjoy!

Hotel Al Ponte Mocenigo is our favorite. Quiet, great staff, beautifully decorated rooms, delicious breakfast, right at the San Stae vaporetto stop, 3rd stop down from the train station. Just returned from our 4th stay there. Best part, the rates are very reasonable for a location right along the Grand Canal, just behind San Stae Church. Short walk over to the Rialto Bridge area, or ride the vaporetto.

We loved staying at Hotel Agli Alboretti in the Dorsoduro neighborhood. Dorsoduro is a quiet location yet very convenient. The hotel is a 1-minute walk from the Accademia Bridge and vaporetto stop. About 10 minutes from Ca Rezzonica and 5 minutes from the Zatterre on the Giudecca Canal. About a 20 minute walk from St. Mark's Basilica.

I don't remember if the hotel bathrooms have bathtubs but it would be worth asking.

Why are you asking about minimal walking? Walking, wandering and getting lost in Venice is the best thing to do. There are interesting and beautiful sights around every corner.

Another area and hotel to check out. After staying in various parts of Venice in the past, including Cannaregio (which we do like), we now try to stay on Campo Santa Maria Formosa (Hotel Palazzo Vitturi, specifically). I like the more neighborhoody vibe, with kids playing in the Campo. It's quite close to the "tourist fray," but not directly in it.

I assume you're asking about a private water dock with minimal walking for when you arrive by train, with your bags. I guess that need depends on the size of your bags.

Hotel Al Ponte Mocenigo and Hotel A La Commedia. We were there in October and I don't think we could turn the AC on at Hotel Mocenigo due to regulations. Not sure what it is like in April. Our room did have a tub/shower combo with half door. Breakfast buffet was good as well as the staff. There is a private water dock and very short walk to the Vaporetto station.

Hotel A La Commedia is in a more crowded area but delightful staff and a rooftop bar with beautiful views. We were able to self control our AC in the room. Also had tub/shower combo. Does not have a private dock but very short walk to a dock where we had booked a water taxi to the airport.

Thank you so much for recommendations! Yes asking about water dock/walking for initial trek with luggage!

Heed what was said about turning on A/C. Just because a hotel has a/c doesn't mean it will be on. The local government decides when hotel a/c can be used and I doubt it will be in April.

You'll find that in quite a few places in Italy.

Since Venice is very walkable, you can walk from the train station to the main square, consider the area near the main train station.
There are some great small hotels and B&Bs there for half of what you stated. Also, if you prefer you can take the vaporetti instead.

Use TripAdvisor.com with its great map feature that show exactly where the lodgings and hotels are located. Also, you can do a search indicating your budget.