29,5% of Poland is trees. Most of those are cultivated forests (so you've got clear markings and roads, some parts are being cut down, some are being reforested etc.), what you're looking for are propably national parks: https://en.wikipedia.org/wiki/National_Parks_of_Poland
those are the real gems.
N-E of Poland is Mazury region. Think "Finland in a bottle". Lots, and lots of lakes and forests, and add tourism.
82% of all forests are public property, so you can come and go as you please, except for fire hazard waring times (during that time you may be prohibited from entering). Camping regulations are a complete unknown to me, desu. But I think you may find those in google easily.