From my experience there is no one size fits all solution here. All countries manage their airspace differently.
Some don't even publish AUP's and instead rely exclusively on NOTAM's for airspace management.
There are however many solutions to make your flight planning an easy task and make sure no F-16's show up on your wing.
For NOTAM info in most of Europe you can use
notaminfo.com
This is a 3rd party site that basically draws area NOTAM's and displays it as a google maps overlay, I still recommend checking for NOTAM validity directly from official sources but this makes it much easier to figure what is relevant and what is not.
And you are in luck, for your relevant area of flight (Poland, Germany and Czechia) all countries publish really good AUP's with graphical interfaces.
Poland:
AUP
Graphical form
Germany:
AUP
Graphical form
Czechia:
AUP
Graphical form
Another solution can also be Austria's AWESOME
home briefing site (Not free) as they not only have a collection of sites for nearby countries as they also give you an option to get a "narrow route briefing" where basically you tell them your route and it automatically gets NOTAM information for your specific route plus a buffer each side (5 or 10 miles, as you prefer).
Anyway hope this helps, let me know if you need more, or for Wx
