I’ve not run capture but have used the HDMI output from the MSO5074 on a handful of display devices with zero drama. Works as advertised, so I should expect it to work well into a capture card too.
The latest firmware bundle includes a VNC server so you could just connect to it that way while still using the device buttons/knobs if desired, but there will be some visual artifacting there just due to VNC. For streaming use, I think your solution should work out just fine.
Here's an example of video I captured via a remote VNC session. Note the tearing due to low refresh rate. HDMI capture should look screen-perfect.
edit: thinking about this, I would expect that both functions could work together for your use case. You can use VNC to give you mouse control over the remote system, you can still use local controls for knobs etc, all while recording output from HDMI for your video edit.