Indeed, a big question is how to make a "lecture" have more value than the text alone. After all, why not just print things up and hand them out?
First, to reiterate the obvious, much practice, a.k.a. "rehearsal", is necessary before one can do all the little things that make a live performance go better than a pre-recorded or lip-synced one. I do think those comparisons are apt.
That is, it's only when you've gone through the material so many times that you can remember it nearly effortlessly that your delivery of it could be natural, fluid, and unhesitant.
About technique: as other answers noted, don't let there be too much absolute-quiet while you're writing. Until you can learn to talk about what you're writing while you're writing it, it is best to write a little, talk a little, write a little. This also lets note-takers catch up. With practice, it seems possible to say a different thing than one is writing, although sometimes one's hand chooses a different syntax than one's hand, resulting in minor grammatical hilarity...
Indeed, be sure to spend most of your time facing the audience, looking people in the eye, etc. So, indeed, this leaves not-so-much time for writing, which, in fact, has (I claim) the excellent outcome that one is forced to choose "highpoints" only, to write, and then "discuss".
Altogether, I'd say write very "telegraphically", meaning no complete sentences, indeed, very few English (e.g.) words. After all, formulas can be written, while sentences can be spoken. The two mediums can complement each other.
I've recently stopped giving long, complicated proofs in lecture (mathematics...), but only giving the highpoints, with complete details available in PDFs on the course web-site. Often, I get the PDFs done in time so that students can either look at them during lecture on a tablet and use some mark-up software, or print them out (!?!) and mark on them.
Handwriting takes practice... Use your whole arm, make big motions. It's not handwriting, but arm-writing.
Every time you get a few critical things written, you can move around (which will result in better breathing, better projection, better connection with audience) and (expressively, both in intonation and body language) elaborate... referring to the on-line or off-line supporting reading material for finer or uglier details.
So, yes, some lower-level technique needs to be practiced, and also some larger-scale viewpoint made very clear in one's mind, so that one knows the "highpoints" vividly, and can nearly-effortlessly summon up and convey them. So, yes, I think it is possible (if one wants it, and if one practices) to make a "live" lecture have much more psychological impact on the audience than a mere text. (Or than reading a text out loud... which is what any sort of slides very easily degenerates into...)