how is it to play poland ?
They are actually one of the stronger countries in the first set of scenarios and (iirc) the recommended country for the tutorials and beginning scenarios. No surprise as the authors are Polish themselves.
Does it have any similarities to Civ 6?
It's more of a numbers and sliders type deal. You set your policies, which all cost resources (in the form of money and "action") and then try and balance the books to create more. It places an emphasis on economic development, GDP growth and HID index. War is executed using progress bars. When you go to war with a country, a window pops open allowing you to select from a variety of different maneouvers. You then see a progress bar - when it's 100% on either country's side, that country is considered to have wont that skirmish. When you win enough skirmishes you have enough leverage to propose a truce and make demands (disarm the country, close their stock exchange, annex them into your country, split up their republic etc).
I've played through all the major scenarios now. They are scripted just enough to keep things on track and interesting whilst giving you complete freedom to play the game in your own style. I'm really hoping they drop a stack of new scenarios as dlc, I had a lot of fun with this one.