Another way to know, or to get close is to try yourself !
You can also read the code of Godot and find out.
A simple test:
in a long enough loop, create a node (or two, which play pong with signals), add a signal to it, make it triggered in a way or another, free the node(s).
Check memory usage with the debugger.
The common "shoot first, ask later" is in dev forums "ask first, try later, in very last resort !"
Trying isn't that hard you know. So you'll get facts over useless speculations.
