Alsace

The wine villages are each different but have similarities and start to run together when you visit one after another after another. I'd give Colmar two days with one full day for Colmar and one day for exploring the Route des Vins. I also really liked Kayserberg, Requiwihr, and Ribeauville.

Colmar is more quaint than Strasbourg and has the Unterlinden museum and its exceptional Isenheim Altarpiece and other underrated exhibits, including Picasso.

I’d go with your plan for 2 nights in Colmar and 2 in Strasbourg so you can also visit Eguisheim/Turckheim which are less than a 15-minute bus ride or easy bike ride from Colmar. I also recommend Riquewihr and Ribeauville which are a 45-minute bus ride from Colmar and just 3 miles from each other. Riquewihr is a walled medieval town
where the word “gourmet” has its origins. Ribeauville is a larger medieval town overseen by its castle ruins. This is the place to visit for its excellent wine cooperative, where you can sample the local vintner’s wines and buy them at very reasonable prices. It’s not common for vintners in the valley to have individual tasting rooms on-site as they do in the Napa Valley. Instead, they have the wine cooperatives.
You can walk or bike on public pathways passing through the vineyards linking Riquewihr and Ribeauville.
Have a great trip!

I'd go with a different plan.
Don't stay in either Strasbourg or Colmar but stay in a nice small town or village.
Why are you visiting Alsace?
Is it to see a big city, Strasbourg or a heavily touristed large town Colmar?

Personally I visited to experience small towns full of 16th century homes, tiny cute wine villages and forested hills full of historic castles/ruins.
Fortunately I couldn't afford the costs of hotels in Colmar and Strasbourg so had to stay in a cute little town within walking distance of the above experiences.

Two days in each isn’t too much.

Egusheim is southwest of Colmar while the other popular villages are northwest of it. A couple villages not already mentioned near Colmar are Kaysersberg and Hunawihr. We walked round trip from Hunawihr to Ribeauvillé and thoroughly enjoyed Ribeauvillé. Near Strasbourg are Obernai and Barr. We enjoyed Obernai more. If you had the time Château du Haut-Kœnigsbourg is very much worth visiting, but I have no idea how to get there using public transportation.

We spent two nights in Equisheim and four in Colmar, taking day trips from it. We had a rental car.

All your replies were so helpful. Thank you.
Tintaldra, I thought of staying in a small village. It seems more difficult to travel around without a car. We do want to go to Equisheim and also the north west villages, one or two. I also found a very resonable airbnb in Colmar. I also hadn't planned on Strasbourg, but a number of people have said it's a charming city and many things to see. Frankly I would rather spend more time in Paris instead but we already have a booked seat to Paris from Strasbourg after 2 days in Stasbourg. Also our airbnb in Paris is booked stiolid around our stay. We could get a new airbnb, but it would involve wasting alot of time in the middle of the day transferring our bags to the other airbnb. I am considering it, though. We would have to pay 20 euros each to change our train ticket, if we could get another ticket when we want it.

I might add that we now have four full days only in Paris, and one of those we would like to go to Chartres. So 3 days in Paris isn't much even if I did spend 8 days there 2 years ago. My friend hasn't been to Europe and I missed a lot in my 8 days.

Eguisheim is just over an hours walk from Colmar, a beautiful village. Kayserberg is not far away either, very beautiful. My first taste of the Alsace many years ago. I had hiked from Ste Marie aux Mines through forests and arrived at the castle above Kayserberg. I climbed the tower and was blown away. I knew then that I would love the area.

NW villages?
Our most recent stay was all in the NW. Less touristed but more suitable for the Alsace experience my wife and I were after.
We travelled there by train from Strasbourg but needed no further transport other than our feet.
Our accommodation was spot on and only 60€ (currently about 70€). Did great meals in their restaurant too.
That experience involved staying in a small town full of 16th C classic Alsatian buildings. Wandering among extensive vinyards. Taking a 15 minute walk to the village that produces perhaps the premier wine of the region. A longer hike to one of the oldest wine villages in the Alsace. Another short walk to another exquisite little wine village. Hiking through glorious forested hills to a number of 13th C castles. A longer hike to a site with an interesting hx dating back over a 1000 years.

I had stayed in Colmar years earlier and found it nice enough. Interesting museum, aesthetically pleasing in certain parts but it didn't really take hold of me unlike the villages, small towns.

I hope you enjoy your travels.