Servos yes. They are standardized these days except with a very few exceptions, Futabs servos have an index tab that needs to be shaved off to fit but otherwise they work just fine with Spektrum and vice versa.

Transmitters and receivers need to come from the same manufacturer or be a 3rd party receiver that's compatible with the specific protocol the transmitter uses and they are all different.
Spektrum and Futaba do not work together.