I would consider enabling all those apart from Annex M, not that it will make any difference at all. I’m just being stupid. PhyR upstream would be brilliant. So would PTM over ADSL2 but I don’t believe that anyone supports it unfortunately. It’s a just-in-case, or in hope, thing.
I’m like you, and so was Burakkucat, who gave me the idea of going ADSL2-only and disabling ADSL2+, exactly as shown. I have extremely long copper lines, ~7.3 km / ~4.55 miles, and I think Burakkucat’s advice was excellent. Tests show that it wasn’t effective in my particular case, for reasons unknown, even though I have the same modem as Burakkucat.
I made that change in the web UI, saved the config file and then loaded the config file into each one of my modems after running a program I wrote in order to make customised copies of the config per modem. This is because I need to set up the admin UI of each modem to listen at a unique IPv4 address per the individual modem, so my program creates an individualised per-modem edited copy of a master config XML file.