Turn on second WAN based on condition of first WAN, or dynamic bonding with highly variable wans

Revisiting an issue/location that I worked on previously.

This year, I’ll have a great solid low-latency low-jitter 100 mbps / 15 mbps dsl connection … some of the time.
However, during peak use time, it may drop to 10 mbps.

Then I’ll have a starlink for backup that is also highly variable between 30 and 250 down, between 5 and 20 up.

The question is: how can I enable the starlink wan when the dsl starts seeing download speed slow?

(I want to use speedfusion so that if either drops offline, my connection will be unbreakable and stay online.)

Dynamic weighted balance despite the wild range of both wans?

Make wan1 primary and wan2 backup and rely on latency cutoff as the single tool to cut traffic over, hoping that wan2 won’t be impacted the same time as wan1?