I guess I should have used the term "tightened up" the borders. When crossing from Romania the real interest was always ownership of the vehicle which took about 2 minutes and didn't require getting out of the car. Crossing into Slovakia has never required a stop and crossing into Austria had never required a stop prior to the migrant issue; but during it there were some lines. I do know that late last year they were checking vehicles in the south and a few people were detained for "human trafficking" meaning they were giving rides to migrants. Daily, PM Orban talks about toughening up the borders even more and at one point the Czechs and Slovaks were sending police to Hungary to assist on the borders. I am certain more to patrol the fences than anything else. At least one good thing came out of this; these countries are working together which isn't common.
All that having been said, how does that affect driving across any of these borders? My point was, I don't know, haven't done it since early last year before the mess exploded. Based on my experience with the bureaucracy and oddities of these countries nothing would surprise me. And if last year is any indication, things can change quickly. I had guests stranded all over the place and one poor individual got on the wrong train and ended up at an internment camp. I am going to have some faith in the Hungarians and say that at worst there might be some delay at the border, but I cant imagine it being bad; and once inside Hungary or Croatia or ..... things should appear as normal and it will be a wonderful trip.
Would I try and make that drive? Naaaaa. Not unless I purchased a Trabant and spent a lot of time figuring out all of the Vignettes between all the points. Remember in every major city you hit it will cost you $20 or more a day to park it.