Best route to take
 

I am planning a trip leaving Toronto on Feb 5th 2023 for Japan (10 days) Taiwan (10 days) Vietnam (20 days - Hanoi, Sapa, Danang, Hue, Hoi An) what would the best order of travel be to minimize backtracking and travel time as well as overall economics.

You probably want to do Vietnam first. Early Feb weather is less hazy and hot than March.
Do Taiwan next. Its geographically in the middle.
Then end with Japan in March (weather is nicer then instead of Feb). But you may be a bit too early for cherry blossoms, which are the second half of March or early April in most places. It would be worth delaying the trip a week or two if possible in order to enjoy the pink tsunami!

Hanoi- Sapa- Hanoi- Hue- Danang (Hoian) (Means of tranportation is flight, train and bus)
No Ha Long Bay or Lan Ha Bay or Bai Tu Long Bay?

Did that last time. But might be worth a second look. Thanks

Thanks. Makes sense.

As far as the economics are concerned , I would first check out the cost of flights to those locations from Toronto and also whether any changes are reasonable. it may be worth looking at flights that stopover in one or more destinations thus removing the need for one or more separate flights within Asia. Eva Air to Hanoi via Taipei might be a viable route or even an around the world ticket. There can also be some bargains to be had with budget airlines within Asia . Having wandered around Asia for many months at a time, I wouldn't worry too much about backtracking. in the greater scheme of things a few hours extra on a plane dent make much difference but a few hundred $$$ in you pocket certainly does.

Weatherwise , I don't think it really matter much which way around you do it.

Of greater importance, is where you go within those countries. Personally, I would skip Sapa and Da Nang. Each to their own but IMO there are far better places to visit in Vietnam. Ten days is a good amount of time for Taiwan but nowhere near enough to do Japan justice. you will need to be very selective.

All are affordable though Vietnam will be the cheapest by far.

Yes Sapa should be in your plan or not it is absolutely up on you. Of course where has beautiful scenery will attract lot of tourists. Many don't want to skip a must-visit place. Ask yourself if it's worth or not. I personally like Sapa. It is easy to get there from Hanoi by train, bus or private transport and it offers enough what I need. There are a lot of choices of accommodations, restaurants etc. If you want to stay in the town centre you stay in hotel. If you want to stay in the village, there are homestays. No problems. Sapa offers you not only tourist hotspots but also something off the beaten path.

Yes not only Sapa but almost destinations now are few tourists in compared with the past. Tourism is just coming back after Covid. Actually Sapa is not a favorite place of Chinese tourists but European or American tourists. Chineses prefer Halong or Da Nang or Nha Trang. Sapa is too exhausted for them.

Several argumentative posts have been deleted as they were an unnecessary distraction.

It would be very useful if you told us where you have been before. How can we answer you without knowing it ?????