Compare the monster transition
here with the raw footage from a workprint
here and tell me that's an in-camera effect. (Edit: The Wikipedia page for
Gryphon Software Morph lists
Bram Stoker's Dracula as one of the movies it was used in – though citation is needed for the claim – so I'm going to assume that's how it was done.)
Shortly afterwards, the workprint also shows Mina without the scar in the shot where it's supposed to vanish, proving that this effect was not achieved practically or by double exposure of the original negative (if it were, no print without the effect would exist – a point you could also make about the transition), but is done optically. (Though it's a very simple optical effect that probably didn't even require a matte.)
The other shot I strongly suspect of being an optical composite is
at 1:55:48 – I think the fringe around the falling figure (which I don't believe you'd get with a simple double exposure – also he'd be transparent) gives it away. And finally, someone on Reddit claims that the blue rings of ghost fire were also done in post, which seems plausible. I do note that the special effects crew listing on IMDB includes a number of credits for "optical supervisor", "optical lineup", "optical effects", etc. ... as well as "digital effects artist (uncredited)".
So while the bulk of the effects (not counting simple cross-fades, which are probably mostly optical) were no doubt done in-camera, I'm also convinced that there are some optical and even computer effects in the film. Probably the
aim was to have it all done without, but in the end there were a handful of shots they just couldn't get any other way.
