Well, I only know English (if you count being from Texas). Ha! I did run into a few places where English wasn’t spoken, but by and large it was ok - especially with Google Translate. I personally found more English the further south I went.
I did make all my train reservations at the same time - it just worked out conveniently for me. And yes, I made them all ahead of time because I like having things sorted out ahead. Whether or not it it’s necessary, I don’t know.
I would say only rent a car if it serves a specific purpose. I liked having mine for staying in Swednica by the Peace Church and driving out to places from there. But it’s not 100% necessary. Somewhere here on the forum is a trip report including going there by minibus public transportation. I think I just used AutoEurope.com to find a rental. Another time I rented from Krakow for 2 days and drove into the mountains south of Krakow to see a few of the wooden churches down there that Carlos’ has written about.
And yes, I just used Google Maps, saving my destinations ahead of time and then downloading Poland as an offline map.
I turn off my home cell and use an Airalo data only eSIM. And then I use WhatsApp for European communication. As long as the other party has WhatsApp also, I can make and receive telephone calls if needed (as well as message).
I am a slow traveler, but I probably spent a day longer in Torun than I really needed - and maybe a day longer in Swednica.
If you are heading to Prague, your order may not be the same as mine. It all depends on transportation….. but Krakow might work fine.
If you scroll through the Poland forum, you will see a lot of great advice and experience! And there’s no right or wrong way - we all travel and prioritize differently. Some people love Warsaw, I love Krakow. Some don’t care for Wroclaw, I do. You will have a great trip!