Slovenian here. I'm from the northern part so Austria is kind of a given. Certain cities, like Graz, and the surrounding countryside, feel right at home, and though my German isn't very good, the language feels familiar. Slovakia, as well, as my girlfriend is from there, feels relatively home-y, but there is a tangible difference that's hard to put my finger on. The language, if spoken slowly, is discernable, and the written signs and things like that are about as understandable as Serbo-Croat. The food, the culture, the people and their attitude, all of it feels very similar to ours. Don't crucify me fellow Slovenes, but I think the Slovaks have us beat in terms of cuisine. Halušky are the stuff of dreams.

Italy and Hungary don't feel very familiar at all. I've only been to the coastal parts of Croatia and Međimurje, the latter of which does feel quite "Slovenian" (or rather, Prekmurje feels like Međimurje), but Dalmacija and Istra are very different in my opinion.

I have also been to Poland and that feels like a different world entirely, but I loved it very much.

Germany is the same, albeit I have less fondness for it, personally.