How to connect two Macs via Target Mode

I want to be able to connect any two Macs together using Target Mode.

What do I specifically need (cable-wise) to achieve this bearing in mind different Macs have difference data ports? Is there a single cable solution or do I need to stock up on a range of them?

Eg. USB-C, Old firewire, new firewire, thunderbolt etc. and perhaps others.

In the old days, it was easy; you only needed a Firewire to Firewire cable for everything.