My question was apparently answered at the other product: https://www.digitec.ch/de...

Thank you for your honourable mention, dear @Mechanicaltux.
I just googled again and in the Vigor 166 gen.1 there is an Intel Lantiq VRX618 DSL chipset. In Gen.2 there is the VRX619 which, as mentioned in my other article, can handle g.Fast up to 212 MHz, the same chipset as in the FritzBox 7583. The 7582 has something older from Broadcom which is also used by the Zyxel and all the g.fast capable devices that Swisscom sells.

I can well imagine that the new VRX619 could deliver a little better values on the same Swisscom lines that only run up to 106MHz anyway.

I have tried almost all g.fast devices including the g.Fast SFP in a Cisco router and only the old FritzBox 7582 with the old Broadcom chipset gave higher values than my Vigor166 gen.1 but only because the DSL driver is tuned a bit more aggressively. Bridge does not work, only PPPoE passthrough and the price 🙈
If you bought the gen.2, post a screenshot of the DSL status page, I'd be interested to see what it looks like.

By the way, the SFP is the absolute worst option of all and negotiates about 20% lower bandwidths than the others, even on my 60m short line. So if you have such an old InternetBox with g.Fast SFP I would want to replace that.