Sure, Ultimate SQM settings: Layer_cake + DSCP marks is a recent thread where we're rehashing some basic ideas.
I think it'd be enough in your case to set up a custom HFSC scheduler on your WAN and set up two classes, say called 10 and 20 each would have say 100 Mbps max. Then you'd classify your ipv4 traffic 10 and ipv6 20. This would handle upload. For download, you could use the IFB method used by SQM scripts and set up the same HFSC scheduler on it, or use the veth method described in above linked thread, and set up HFSC on that.
Here's a blog post on my blog about HFSC with an example set of tc commands:
http://models.street-artists.org/2018/01/16/understanding-hfsc-in-linux-qos/