2x IPv6 /60 delegations, for 2x routers/gateways ?

I have the 1Gb Residential xFinity package, with a MB8600 modem and a Ubiquiti USG in front of my home network, and an ipv6 /64 delegation to my USG. All works fine, for a single VLAN.

Now I want to do two things:

1: split out a few VLANs for my home network, to separate things like IoT devices, my VoIP traffic, my wired NAS+desktops, etc

2: add another gateway (likely another USG) for a highly isolated work office/lab network, IPv6 *only* (no need for another public IPv4 address).  Will also need multiple VLANs/subnets inside this work/lab environment.

For #1, I believe I just need to increase the PD hint to /60

For #2, I plan to add a small unmanaged switch behind the modem, connect in the existing USG, then add a second USG to the switch. I would then configure the second USG with no DHCPv4, and set the IPv6 PD delegation size to /60.

Before I just start experimenting, figured I'd ask a few questions here, hoping to find poiners to "official" docs or statements from Comcast:

A: Does xFinity officially support /60 prefix delegation, for scenario #1 above?  I found a few comments in the forums, but they seem experimentally observed, not necessarily official.

B: Would xFinity allow me to request a 2nd /60 for a 2nd gateway behind the same modem, for scenario #2 above?

Thank you