An incomplete answer - I bought the Lumen lights with the DRL light bar that you linked to, but have not fitted them yet. I tested them on the bench, they seem bright and are intelligently designed so that when the turn signal powers on the light bar turns amber, and won't go back to white until the turn signal stops flashing.
My 2020 build US spec M3W does not turn on the headlights with the ignition unlike yours, oddly enough, so I had planned to use the side-light wiring for the DRL. As far as I can tell in my car, the wiring is there but does not do anything, so I can convert it to an ignition-on circuit and then control the headlamps with the switch. I already added a new relay for ignition-switched power as I added some yellow fog lamps as DRLs already (you can use the heated seat fuse as a source of ignition-on power to control the relay), and plan to use that for the light bar. Not sure I see the need to remove the existing turn signals.
Not sure what the best solution is to have switchable headlights without re-wiring the dash, unless someone else has worked this one out. Perhaps add another switch under the dash?
