Sorry, but all this has already been answered.
MC told you already that all USB3 cards are fully backward compatible.
And in regards to better directly take an USB3 card ... isn't it obvious why ? PCIe sockets are limited resources in every PC. I would take an USB3 card as proposed, so that the card - from time to time - can also serve other purposes, like backup.
Additional tip: to fully isolate the recording interface behind this controller I would only connect the recording interface to it.
You can also preconnect an USB3 disk to it, but I would keep it turned off, so that nothing can interfere with audio transfers.
If you perform a backup then you will surely not do any recording, then turn on any potential USB backup disk, perform the backup and once the backup has been performed, turn it off again, so that only the recording device is active behind your new USB3 interface.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14