I had short visit to Warsaw years ago, driving from Lublin returning via Bydgoszcz which we enjoyed.
I have not been to Bydgoszcz or any of the popular sightseeing areas. Trying to plan a trip to include all interesting places. Would spend 7 to 9 days taking day trips with overnight stops (4 nights) in some places. Would this be easy to plan without booking a tour? I have looked at several Poland escorted 8 day tours from Bydgoszcz most include Warsaw for 4 nights. Some offer accommodations at popular hotels. I would not need to return to Warsaw and can take flights local airports. If I decide doing trip independently (solo) taking public transportation from Bydgoszcz or some day bus tours would this be difficult? Would plan from June to August.

We drove through SE Poland, starting and ending in Krakow. You can read the trip report by clicking on my name and then "Finding Trip Reports."

There is not much in Bydgoszcz - it has a small old city section - but not really much going on ... You can take a bus or a train to Torun ( which has larger old city and much history back to Copernicus days ) ... Ciechocinek 24 km more south from Torun is a spa city - small but nice to walk around ... Bus would be my recommendation ( where Ciechocinek can only be reached by bus ) and in Torun - main bus station is near the center ...