Thunderbolt comes with multiple advantages over USB 3.x/c, but whether or not those advantages matter depends on the devices.  If they're working fine over USB currently, there won't be much advantage unless one or more of the devices involves video output or ultra-high performance (NVMe) storage, among others.  Then the speed advantage of Thunderbolt over USB comes into play, just as it does with video output (it's far more flexible with chaining displays, ultra-resolution monitors, etc. than USB 3.x by itself).  
I just got an XPS 17 (9710) which has four Thunderbolt 4 connectors on it. I have no Thunderbolt 4 devices, but I have lots of regular USB devices to connect. I do not need a docking station and will not be using a second screen. I just need to connect all my existing USB hubs and devices to this new machine. The local electronics shop has some Thunderbolt 3 to USB-C connector cables ($45 from StarTech). They appear mechanically the same as Thunderbolt 4 but ... what am I giving up or losing or missing if I use a T3 cable instead of a T4 cable?
Thunderbolt 4 Connectors