Any question answered...

pierogi

Was disappointing but we didn't do much research on the restaurant so might have been our mistake.

Krakow is small, so do everything on foot. We did two free tours (jewish one and old town) which were excellent.

Cheap but excellent beer, Zubrowka for wodka. Stay away from the flavor wodka's, they're good for a taste but not for an entire night.

You can visit Wawel castle for free, but there is also a paid tour. Stroll around the Kazimierz district.

If there's snow, the park that follows the ring around the city.

There's also good museums but we didn't visit them unfortunately.

Avoid posh bars, go to the locals. There was one which was awesome, I'll try to find the name. Lot's of craft beers on tap + awesome barman.

My ex went recently, and had to ask the restaurant for pierogi as a special order - most of the cuisine was modern European, rather than trad Polak.
I went years ago (in the 90s), as a student. At the time we could afford to hire a taxi driver for a day to take us to Auschwitz and hang about while we had a look around before bringing us back.
I'm not sure that a taxi driver is so affordable these days.
Either way, if you decide to go, it'll do little to brighten up your day.
It isn't an experience which I would care to repeat.
I'll be surprised however, if it leaves you without making an impression upon you.

@JurekB makes an excellent suggestion. I met a mate at Katowice airport and we hired a car and drove to Auschwitz. I would highly recommend a visit there, seeing TV documentaries doesn't beat the real experience.

To counter, I've heard less great things about the Auschwitz "experience" recently. I'll see if I can find a link.

Edit: https://www.tabletmag.com/jewish-life-and-religion/297164/never-again-will-i-visit-auschwitz
On my phone it's only showing me the first half of it though.