Thread size is 3/8NF24. Yes they are bubble flares. You might have to search a bit to find connectors for bubble flares, more commonly available for double flares …
I wouldn't do this. Tampering with brakes, removing designated safety devices, not a good idea. Don’t tell your insurance company or registration authority.
In my experience the PDWA is simple, robust and reliable. If it is not working should be easily fixed by pulling it apart, cleaning thoroughly, if the NLA square section o-rings are deteriorated, replace them with circular section rings that are not a tight fit.
There is a lot more variation that just the type of flare. Notice in your diagram, the double flare nut has thread all the way to the end while the bubble flare nut has a spigot. My understanding, it used to be most commonly the other way around while these days spigoted nuts are used almost universally, including for double flare connections because there is then no requirement to cut thread below the top of the inverted taper (cone). Notice in your diagram, the hole for the bubble flare nut has a reduced diameter below the thread to accommodate the spigoted end of the flare nut. If a spigoted nut is used in a hole without this reduced diameter (i.e. a fully threaded hole) there is risk that over-tightening the nut will spread the spigot making it irremovable; example in the photo.
Note in yr diagram, the bubble flare nut has a protruding taper on the end of the spigot. I have never seen this before, older style had the opposite, inverted taper, newer nuts have virtually no taper and the spigots are less likely to spread …
