Not many do bitumen waterproofing membranes anymore, mostly just put a Katja down before the screed and that's it.
Guess what the "Katja" is made of
Whether self-adhesive or welded is up to the processor's calculation. The self-adhesive only has technical advantages on substrates that cannot tolerate the temperature of welding.
By the way, the work is for fools. Anyone interested in doing it themselves can easily spend a weekend on this.