We did a fair drive yesterday, again on the backroads. One thing about Czechia is that there are lots of paved backroads that are easily passable by all vehicles. No need at all to get on the freeways if you're not in a rush to get anywhere.
And, the freeways in Czechia are all toll roads. You need to buy what they call a "vignette" in advance. It's essentially an e-pass that registers your vehicle's licence plate. Many European countries have this system in one form or another, but sometimes it's just for heavy trucks, and sometimes it's for all vehicles. You need to check each country in advance to see what the rules are.