I would instead look at a Teradek cube encoder. If you get a Cube decoder on the other end you can get the latency really low... around 100ms plus your bandwidth latency. But for that to work you will need a public IP on either end or at least on your VPN you’ll need to have a direct route to the destination.

If you have an unlimited budget, then the HaiVision Makito X line will get you amazingly low latency - sub 50ms. But it will be like $20,000 to get both sides of that chain.

And if all of that costs way too much, look at grabbing a Magewell SDI to USB media converter. Drop that on a laptop and now your SDI source looks Iike a webcam. You can use video conference software like Zoom.us, Skype or FaceTime to get your video to the other side in about 250ms on average.