I scanned through various reporting for the same question. They tested 3 brands of cheap disposable vape (article cites there being something like 100 brands of disposable vape on the market). Pretty sure these are all-in-one units; I don't even think they have pod cartridges—so you use it and throw the whole thing out, batteries and hardware included. So they would have incentive to be the cheapest components possible and to cut corners. There’s a line in one of the articles that said something like they have worse chemicals than cigarettes which are worse than refillable vapes, suggesting these are bad, cigarettes bad, refillable less bad to some undefined degree. While they mention the vape liquid as a cause a little bit, a lot of the bad stuff seems to be coming off the hardware with heat—so like leaded wires and atomizers with bad metals on or near them.

All that to say that as per usual reporting tries to lump all vaping into this one mysterious bad category (thinking here about how that stuff with off-market internet THC vapes was used to support headlines like “vaping destroying lungs of zoomers overnight”). I doubt vaping is safe, but even so I would prefer clear and transparent info about it, and often it seems like there’s just a policy decision/agenda-driven bent to a lot of the reporting.

My guess is that if you get a larger system with better quality parts, it’s going to be safer generally than smaller/and more disposable oriented stuff.