I own a Quad2 and SDI 4k (also an Intensity Pro 4k I keep offsite, and an ancient PCIe HD-SDI that I use at the office) cards and they work perfectly in OBS. Each input is selectable as it's own entity, as BMD intended. If you have any more questions or want some screenshots, please let me know.
@SumDim, I find it a bit odd that you would be so vehement in your replies. When spending this much money it's really important to do research and that's what Stolkie is doing, so please don't try to discourage that. Also you'll never get in writing a guarantee that any hardware will work with 3rd party software (because they have no control over it) so even trying to ask for that, or even state that as an means of making sure the card works is ridiculous on all levels.
To address SumDim's point though, you can buy the card from a reputable dealer and before you buy it tell them what's going on. If they don't have one already in place they may be able to give you (if you're really concerned) a 100% return refund policy...you should get
that in writing
before buying the product.
Really the biggest thing with these cards is making sure they work outside of OBS. If they work with the BMD-supplied testing software, then they will work in OBS (at least that's been true for me and the people I help 100% of the time). So make sure that your MB has the correct slot for that card (i.e. Electrical
and Physical lanes), and said slot is running off the CPU PCIe lanes, not the southbridge/chipset lanes.