Sounds like a very ambitious trip. If it were my holiday, I'd cut the number of countries by half. So to spend a least 2 weeks per country.
I've made several trips all over Poland over the years, so I will note the southern Poland (basically everything south of Łódź) by itself can easily take up two weeks by itself. Looking at the map, you'll see the region (stretching from Germany to the west along Czechia and Slovakia, to Ukraine in the east) is as big as some of the countries you are visiting like Slovakia and Hungary. There are several different mountain ranges in Southern Poland, each a microcosm with their own character, cultures, and history:
Bieszczady Mountains: On the very east, along the border of Poland and Ukraine, you have the Bieszczady National Park (a UNESCO World Heritage Site), this is the most wild and rugged parts of the country, home to primeval forests, ancient wooden churches, bears, bison, and wolves. It's long been on my to-do list, but the war in Ukraine has put it on hold for now.
Tatra Mountains: This area, based around the popular resort town of Zakopane, is probably the most accessible from Krakow. This is also home to the unique Polish highlander culture (Górale). Many good hikes of all abilities accessible from Zakopane as it is surrounded by high peaks, including to the glacial lake of Morskie Oko, a must see.
Beskidy Mountains: This is the point where Slovakia, Czechia, and Poland meet, and has become a popular alternative for locals rather than the more touristy Zakopane area. The mountains here are not so tall and more manageable than the high Tatras. I suggest staying in the spa town of Wisła. Next to Wisła is the larger spa town of Ustroń also good to stay in.
Sudeten Mountains: This area is to the far west closer to Germany, a landscape dotted with forgotten medieval villages, baroque spa towns, and grand old castles. This historical-cultural region, know as Silesia, has been at the center of a constant tug-of-war since the middle ages, between the Germans, the Poles, the Czechs, and the Austrians. You can base yourselves in the charming Kłodzko Valley.
Personally, for what you are interested I'd suggest a week in Zakopane in the Tatras and a week in the Kłodzko Valley in the Sudetes. Here's my trip report and photos from my Polish Sudeten Mountains roadtrip + some of the surrounding Silesia region - https://community.ricksteves.com/travel-forum/general-europe/vicarious-travel-poland-2017-wroclaw-silesia
You're still 1 year out from the trip. I'm sure better flights might pop up. Thinking best to fly in to Krakow (or Katowice) and out of Budapest. You might find Frankfurt as a good connection to get into/out of Europe.
Hope this all helps :)