This is my observation for Digi Home fiber on TM infra.

1. IPv6 address on WAN
Yes
2. Public IP or CGNAT IP on WAN
CGNAT for IPv4 only.
3. Do they use PPPoE, DHCP or Static on the WAN interface
PPPoE
4. Static or Dynamic Prefix Delegation for LAN (/56 or /64)
/64 for WAN (IPv6 Prefix), another /64 for LAN (IPv6 delegate prefix)
5. In terms of speed and stability, how good or bad is their IPv6 routing
Honestly not sure, seems to be ok for local websites
6. Own router with custom firmware with their service (Merlin, Mikrotik, OpenWRT, DD-WRT, PFSense, OPNSense, etc)
Used previously with ZTE router, eventually upgraded to TPLink and now using AsusWRT. No issue getting ipv6 assignment