Ive been splitboarding for a few years and mixed in some ski mountaineering lately because of the light gear for the longest trips.
I think you can be confident that a higher cadence and shorter steps wins in the long run. Its less fatiguing.
Some of the pros with hardboots is that they often have a larger range of motion than softboots, which allows for longer strides. But it doesnt mean you should do so. However, a good thing is that its less likely you need to use the heel climb wire/support which saves time.
Generally speaking there are def. some advantages using hardboots vs softboots for sure. But it has cons as well.
ve sensed that the splitboard community is a bit behind ski touring with regards to efficieny/training, probably because more people ski tour and it has been around for longer. Also, in the splitboard community its not that common to do structured training and most people dont think that far wrt optimizing as you probably do -since youre a member here. (Please dont get me wrong – I love splitboarding).