I have never tried that. We use it to share powerpoints in meetings or do troubleshooting together. Or I use it to do family video calls with the kids. Fps are never an issue. There are times where there are compression artifacts tho. Especially if someone have a bad or variable connection. On a buss or a train or similar.
Ipv4 is not even ipv4 compatible. You use nat to translate one type of ipv4 into another to talk on the internet. Ipv6 is using nat in the same way.
The problem is that ipv4 is not forward compatible ( naturally ). So ipv6 can talk to both, ipv4 only to ipv4.