That's a really odd question, since both Thunderbolt 4 and USB-C use the same type of connector. Anything that fits in one will fit in the other and work.
Thunderbolt 4 is of course faster and can offer more options than the regular USB-C, however the M1 iMac does not have Thunderbolt 4 ports. It has two Thunderbolt 3 ports and two USB-C ports.
When connecting the Hub, its own speed will determine what the port will do. If you get a USB 3.1 Hub it will limit both the USB-C and Thunderbolt 3 ports to USB 3.1 speeds.
If you want the fastest transfer speed, look for a Hub / Dock that offers Ultra High speed SD over Thunderbolt. Like this one: link-> Belkin Thunderbolt 3 Dock Pro - Apple
or this one: link-> https://eshop.macsales.com/shop/docks/owc-thunderbolt-3-dock
You can use the Thunderbolt 3 ports if you need to connect Thunderbolt capable Displays through the dock.