There’s no “golden rule” for this sort of thing. I believe (There is room for error here) that all jumping normals hit high, but jumping specials usually do not. Also, I’m not a fan of the term “overhead”. It’s a little bit confusing. I prefer:
Hits High: Must be blocked standing
Hits mid: Can be blocked standing or crouching
Hits Low: Must be blocked crouching
Other definitions that include things like “high attacks which on crouchers, while overheads hit them” is needlessly overcomplicated and creates too many exceptions (a given move might whiff on a crouching Cammy but hit a crouching Zangief. Now what? )
If you look at the Shoryuken Wiki for SSF4, you will see that unique moves/specials for each character that hit high or low are marked as such. Otherwise, it’s safe to assume that if your opponent is doing a jump normal, it also hits high.