It is questionable which values you are referring to. Do you mean the DSL Actual Rate - i.e. the data rate at which the DSL line itself is operated, or do you mean the net data throughput to the Internet?

The two available modem codes have not shown any significant difference on my g.Fast connection, which is operated by Swisscom like all the others in the country. The STD firmware package with 123210_30 runs very stable at DSL actual rate 580 MBit/s on an approx. 50m long line. It depends a bit on the weather, but most of all on the temperature of the modem itself. The cooler the better, lives in a cupboard with an active fan.
No transmission errors, not even FEC, rock solid for over a year.

I would guess that the line from the UP box to your modem is not ideal. In addition, the flat telephone box included with the modem is very disadvantageous. A twisted pair line brings a very clear improvement.

A completely different story is the net throughput to the Internet. Besides all the usual factors, swisscom automatically shapes and limits the throughput they leave for you via their BNG (Broadband Network Gateway).
I've had such fun that depending on the MAC address requesting the DHCP lease, my upstream was halved. Then, every time the MAC changes, your connection is put into a kind of test mode where the downstream is also severely limited.
You won't see this in the real negotiated DSL sync rates, but they simply limit your throughput. Also, Vigor doesn't talk to their equipment on their site about remote maintenance and advanced diagnostics features, and many employees think something is broken.
Anyway, just leave it on and let it run. Even with the Vigor on, this limited "grooming" phase will end at some point and you won't be artificially limited any further. As long as they don't see in the counters on their side that there are increased transmission errors or disconnections. A restart and resync of the DSL can quickly trigger this after a few times a day.

With the Wingo subscription through which this runs, I achieve 545Mbps/115Mbps at speedtest.net, for example.

Unfortunately, we do not have any real empirical data on this. We have forwarded the question to our community and hope that a user can provide input.