This applies to the Saffire Range
The Saffire range will work with Thunderbolt 1/2 (DisplayPort) and Thunderbolt 3 (Type-C) ports.
To set this up on a system with a Thunderbolt 1/2 port, you will need a Thunderbolt to FireWire adapter and a FireWire 800 to 400 cable.
In order to set this up on a system with a Thunderbolt 3 port, you will need a Thunderbolt 3 to 2 adapter, a Thunderbolt to FireWire adapter and a FireWire 800 to 400 cable.
The performance will not change when using these adapters.
If you cannot see the Saffire in Saffire Mix Control on macOS 10.13+ please see the following article:
My Clarett / Saffire / Red Interface isn't working on Catalina / Mojave / High Sierra
Please also ensure that your computer is compatible with your Saffire:
Focusrite product compatibility - Windows 10
Focusrite product compatibility - macOS