What level of tethering are you looking for? What tethering have you used before? You can do the Lightroom Plugin for free or there's a larger Image Transmitter 2 package for purchase. Based on reviews here, I'd stay with the free plugin. It's a basic image transfer, so no settings / live view / control from the laptop.
Windows 7 is fine - nothing that requires Win8 or Win10. There is also the Flu card, but I'd stay away from using anything more than a S-JPEG with it.
Yes, tethering is a weak spot, yes, it sucks that CaptureOne doesn't support it. It's part of the whole price point - everything is a trade off.