Custom interfaces question

Hi there! 

Wanted to clarify one thing on custom interface usage.

We can create any number of new interfaces through the Explorer menu (ctrl+E). The question is if creating 10-20 new interfaces (wtih 10-20 buttons in them, so.. a lot of assets) can have a performance hit on the player PC?

Because if I understand correctly, all interfaces(connected to chacracter) load in memory on character loading in scene and stay loaded no matter if interface is showing or hidden. Or am wrong on this and it is ok to use any number of custom interfaces?

any infos about this?