Thanks, Francois, for the links – I read over these and looked at the help files regarding properties. Still, it’s all very technical and not sure I truly understand all of it.
I do have some experience with mixing video taken with different record modes. I own a Sony fdrx3000 Action Cam and if I allow Vegas to match project video settings I get a slightly different setting:

What I have done is use the XA10 settings for both and my renders look fine. I render for sharing using the Main Concept Internet HD 1080p for immediate sharing and eventually Sony Blu-ray 1920×1080-60i, 18 Mbps video stream to produce the Blu-ray. Maybe that was a mistake but I couldn’t see or hear any issues.
My question is if I continue to use the XA10 and purchase the XA40, would it be better to use the XA40’s project settings? In fact, does it even make any difference in this specific case. I am not interested in the 4K mode but likely would use 1920×1080 (35 Mbps) at 29.97P frame rate. I would produce a Blu-ray from these mixed cams.

J. Paul
Win 10 Home Prem x64 VegasPro 13
Canon XA10