Thanks for all the info. That is some good research to be sure!
I would imagine that the majority of the "Sex work in some capacity" would be at lap dancing / pole dancing type venues. Also adult modelling. Cam work etc. There's probably a lot doing those types of sex work. It's hard to guestimate percentages based on my own limited experiences of being dragged along to lap dancing venues by my mate a couple of times. I genuinely find such places deeply embarrassing and they make me very uncomfortable, but I'd guess that practically all of the young ladies there were definitely university students or uni student age.
There used to be a 'Little Black Book' online guide to, ahem, "gentlemen's massage parlours" in the region, and I admit to browsing that 'book' a few times. I guess it was kind of 50/50 regarding the age range, with roughly 50% being over 30s females, and the other 50% being uni student age young women. There used to be a lot of such venues in this city, each with its own website with photos of the girls etc, linked from the LBB. but I don't know if 80% or so of them have closed down, because the LBB no longer seems to work properly/hasnt been updated in years and is full of dead links. And most of the former massage parlours no longer have websites. I don't know if that means they have closed down, or just gone more secretive. (Or they might just have changed their names, I don't know what has happened tbh.)
tl;dr I think a lot more more students work in the lap dancing / pole dancing clubs than in actual prostitution. But there's probably much more in modelling or cam-work. But that estimate is only based on my own very limited experience. Back from when it was possible to sometimes see photos of the girls or women who worked in the parlours, on their websites, and you'd have their ages listed too. Although Most of the ages stated were probably actual age minus 10 years, for the older ladies.. Judging by the photos at least!
I JUST EDITED: the whole post with a couple more new thoughts, and: Regarding your last point, some of those that are in various niches of the 'industry' of their own free will, can earn extremely good money, as escorts, or in the lap dancing clubs. The same almost certainly goes for adult models or cam girls too. Although I have heard that a lot of porn actresses can get mentally scarred by being in that particular part of the industry. But much less so for solo posing for photos and videos in provocative poses and outfits etc, AFAIK. Then there's the whole ethical porn niche, which I would imagine prioritises the mental well-being of the ladies involved.
If these women are comfortable with what they are doing, they are probably a lot more successful at the capitalist game than many, and could be making a lot of money if they had the good fortune to be born with highly desirable looks and bodies, and have chosen to very directly cash in on that, while they still can.
If a feminist saw this post they'd probably wipe the floor with me, but it's just as I see things, from a male perspective.