I had to look up "Backpressure Turbine" because in shipping, that kind of set-up is basically never used thus the term was unfamiliar to me.
STAL-Laval on the other hand, although I never worked with them (never even saw one) were studied in-depth back in nautical college as they were back then regarded as the pinnacle of compactness (power vs size) but in fact actually were relatively rarely used in ships: the compactness only was in the turbine itself, the boiler and condenser installation still was HUGE, as were the required fuel volumes, which a ship has to bring along... People somehow completely overlooked the fact that where fuel is, no cargo can be, in the late '60's and early '70's

Back when I went to college (mid/late '80's), educations and competency certifications and such were lagging behind by about 10 years on actual technological trends, so there was still quite a bit of emphasis on steam while by then it was allready clear that steam turbines as a marine propulsion principle was over and done for.
During my career I have mainly operated steam as a pure heating medium, only once for power, and that was only the cargopumps.