3 weeks in Poland Itinerary

We've only been once, but visited all those cities, and we didn't drive.

Aren't you doubling back with Torun-Gdansk-Poznan/Wroclaw? How about train from Warsaw to Gdansk (it's a high speed route), then work south by car?

I'm not anti-car by any means (I drive in another country of Europe practically every day), but if you're only seeing the cities, a car might not be necessary - and could be an hindrance in places - but if you're planning lots of stops along the way it makes sense. There were a couple of day-trips we skipped because public transport was too inconvenient.

Because people's travel styles are so different, I'm not sure the following helps; nevertheless, we spent 4 nights in Warsaw (but no Treblinka visit), 5 in Gdansk, 2 in Torun, 4 in Poznan, 1 in Wroclaw (just a stop to break the long journey - it was clearly worth more time) and 5 in Krakow (but no salt mine visit). That worked brilliantly for us. Jet lag wasn't an issue, though.

https://community.ricksteves.com/travel-forum/trip-reports/poland-first-trip

It's very doable - the only question is -- will there be enough time for you do everything you'd like to. Without knowing your interests, it's difficult to comment but we are planning a similiar trip for the fall and, like you, I've spent hours planning an itinerary.
Below, I've jotted down the major (unique) sites, in hopes that this will help your planning, and provided some thoughts. The drives time is from Google but, in the past, I've ended up taking at least 30 mins more than Google estimated-.

Day. Town. Drive Time. Things. To do
1 Arrive

2 Rest Day

3 Warsaw Royal Route palaces/Old Town

4 Warsaw History of Polish Jews

5 Warsaw Warsaw Uprising Museum

6 Treblinka

7 Drive to Torun 2 1/2 hours Old Town

8 Torun Copernicus, Teutonic Knights castle, Cathedral

note - Are you going to Torun to break the drive or because you want to see Torun? We debated this and decided to spend extra time in Gdansk, to simply enjoy Gdansk and visit Westplatte, Stutthof, Oliwa and/or the tri-city area.

9 Drive to Gdansk 1 1/2 hours Old Town

10 Gdansk WW2 Museum
11 Malbork Castle Castle
12 Gdansk Solidarity Center

13 Wroclaw 5 hours to Wroclaw 3 1/2 hours to Poznan W - Old Town/Cathedral Island P=Old Town/Imperial castle
14 P or W W - City Museum/Cathedral P. ??

note - we thought that Wroclaw would have more to offer than Poznan. And - is it simply intended as a stamp-over or are there things you really want too do? Would it be better to spend an added day in Krakow??

15 Drive to Krakow 3 hours from Wroclaw 5 hours to Poznan Old Town

16 Krakow Castle Grounds/Cathedral

17 Krakow Jewish Quarter/Schindler Factory

18 Salt Mine Salt Mine

19 Auschwicz Auschwitz

We will (as you've guessed) be staying in Krakow a bit longer to see --Częstochowa, Nowa Huta, Home Army Museum, Rynek Underground, National Museum, etc.

20 Return to Warsaw

21 Depart Warsaw

Whatever you do, have a wonderful time!!

Just returned from 2 weeks in Poland last week. Seriously consider taking the trains. They are as easy as anywhere else in Europe. We went Gdansk - Wroclaw - Krakow - Warsaw via rail. You can easily take a train from Gdansk to Malbork (we did).

If I had to plan it again, I would spend less time in Warsaw. Unless you are planning a trip to the beach in Sopot from Gdansk, you might want to shorten your visit. Gdansk is pretty small.

If you do decide to drive, I'd take 1 day from Warsaw and 1 day from Gdansk and go to Zakopane. I wish we would have done so.

I wouldn't cut down your time in Warsaw, there is plenty to do in less than 3 full days. I have to agree with the other post about driving vs. taking trains. If you are going to drive, then see some out of the way places (like Kazimierz Dolny) that would actually take advantage of having a car. The main cities are really well connected by trains, which are quite inexpensive.

Kazimierz Dolny is probably the most overrated city in Poland...

Number 9. Poznan or Wroclaw - definitely Wroclaw! Better atmosphere, lower prices, great attractions and easier to get around. Also, Wroclaw seems better for a romantic couple trip than Poznan (which is more business-like to me).

Here are some great tips on travelling in southern Poland: https://overhere.eu/blog/9-best-places-to-visit-in-southern-poland/