My understanding is that, for example: If I want to transfer files at 10Gb/s from my PC to my NAS.
I have a Router with only 1Gb/s networking and use that 1Gb/s port to plug into a switch. That switch has to have at least 2x 10Gb/s port which I use to plug both the PC and the NAS into the switch's 2x 10Gb/s ports (assuming that both the PC and the NAS also have 10Gb/s capable networking hardware). Then I will achieve 10Gb/s between the PC/NAS?
The router is irrelevant, if both the NAS and the PC are connected directly to the switch. Other than that, yes.