Well, that's particularly interesting, as I wasn't aware that ArtelW had released all those old models, and I
do happen to have my own 3D printer these days (which isn't all that busy at the moment, partly because I'm still waiting for much of the resin I ordered - I have alternatives, but I don't entirely want to use them up on stuff that would be better done by the resin that hasn't arrived)
While I'm not a fan of everything in that pack, there'd certainly be something to be said for printing out an Eldar or two...
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As far as the scaling, one thing I've been doing so far is exploiting the fact that I've done 3D scans of some of my models; I can load the scans into the editor and scale them based on known dimensions (usually that they have a 40mm base), and then compare the sizes there. As such, it is possible to do the comparisons pre-print, with less guesswork as far as how big they actually need to be.
EDIT: For example, for the Eldar Farseer, I can compare to a known model and say that a 1.6 scale factor would be a reasonable-ish sizing. (Possibly a
little big, so I might actually go 1.55 or so. Eldar are meant to be taller than humans, but maybe not quite so much).

With that in mind, it might be worth scanning in a known model to use as reference.