Hello, Slender,
So, 1.5 years later, I’ve picked up on a few things:
Overlap functions are native Engine functions; they are handed by C++, directly, and not calculated with a virtual machine. As such, they are VERY fast and pretty cheap. The only time you run into trouble is if you have many actors calling many overlaps over and over in quick succession.
Yes, they are tick functions, but they are native, inexpensive tick functions. You can put dozens of them before you find any real consequence.