So far as I know, no one is offering moves to their copper services, of any variety, so there are no comparisons to be made.
Correct.
There are no new copper PSTN services, they have been unavailable for over 2 years, the last orders for such things were in 2023.
Those people that already have one and also have ADSL / VDSL or some other broadband product delivered over copper are already being migrated to VoIP service, which for the majority just involves unplugging the phone from the Openreach socket and plugging it into the broadband router instead. Some might receive a new router as part of that, although most routers provided in the last several years already have the socket for a telephone.
For a tiny minority of devices which inexplicably still require ye olde copper phone line which is powered 24/7, there is a bizarre product called SOTAP Analogue, which is basically an ATA installed in the street cabinet so that at the consumer end it looks like an old phone line, powered from the cabinet, but converted to VoIP in the cabinet and then carried over fibre. That won't be available for long, it's only intended for the few ancient devices such as security systems and emergency 'I've fallen and can't get up' calling affairs - all of which should have been replaced with modern equivalents years ago anyway.
Any requests for new service will be provisioned as VoIP. The vast majority of those will be a broadband product with the 'landline' as a add on product if people want it.
For the tiny minority who want a 'landline' but do not want Internet access of any kind, they will get a cut down router which only has facilities for a phone, which can either be some old style piece plugged in, or more likely a modern item which connects direct to the router via DECT. Such services will be extremely limited (as in most providers won't offer them), and they will be expensive.
As for the competition - Virgin Media stopped provisioning voice services over copper years ago, all of those are the same plug the phone into the router deal.
Others such as City Fibre and Gigaclear only operate fibre networks, so there never was any copper option there and never will be.