ESP32 vs ESP8266 library compatibity

[Cool Javelin]

Hello:

Are all libraries for either the ESP32 or the ESP8266 freely interchangeable?

Since the Arduino will compile the library routines into the appropriate machine code for the machine, and from what I have seen, all the code in the libraries is in C (or C++,) can I use any library with either device?

For example: the ESP8266FTPServer.h. Can I use that on the ESP32?

Are there libraries that are not interchangeable? If so, how can I tell which ones are and which ones are not interchangeable?

Thanks, Mark.