What audio delay is required to sync audio to video? I have 500 milliseconds max on my mixer.

I'm not an expert technician but I installed the card, configured it for 4 inputs (3 are cameras and one is a graphical feed from ProPresenter) and no audio through the card. I have a separate USB audio interface. The audio and video come together in Wirestream Pro. I did not have to add any delays in order to have the output from Wirestream synch'd. Images of the lips and audio of songs and speech seem perfectly aligned.

Does this work with OBS ?

Works perfectly with OBS. As long as the computer it is running on has the resources, it will work very well with OBS and Resolve.

The gaming computer that we purchased does not have an expansion slot in the computer and it can not be returned. It has 2 3.0 ssusb. Options?

How many inputs or outputs do you need? Magewell makes quality USB 3.0 capture dongles, with HDMI or SDI (one input per unit). Depending on your needs, perhaps NDI might be an option - NDI from Newtek is a FREE way to get IP video over your network, for instance video from one computer to another, or send gaming video out over network to another computer running OBS or something.

Does anyone know how to get 1080p to work into Vmix? Every other format works in vmix but 1080p does not work.

Once installed you will need to get the black magic drivers installed as well and run the software once. From there in vmix you will need to make sure your project file is set correctly to 1080p 30 frames or 60 depending on recording or stream and your internet speed. Once that is set you can add a camera source on from the list. If done correctly you should see them listed as Decklink Duo 1, 2, 3, or 4. Make sure wen you are adding your source that it reads the cameras output correctly. It is super important that the camera and the project file match or higher then what the camera is outputting to the sdi or it will give you problems. Another tip I can give you to test the camera is to use the black magic software to preview the camera output to gather your settings.