E.g for a conferences last year I made this presentation (please ignore content) https://flurdy.github.io/scaling-scala/ in just one page: https://github.com/flurdy/scaling-scala/blob/master/index.ht...
Currently I end up just doing a lot of the graphics in Inkscape, splitting the layers into multiple SVG files (one per layer) using a script I found, and then assembling it together in Reveal.js using fragments. This technique I used most in one of my latest talks: https://sinusoid.es/talks/immer-meetup17
Now I wonder if maybe I just want to use something like Keynote... but I only use GNU/Linux and try to live in a mostly libre environment. Maybe Impress is good enough?
it was also a bit slow to load, on my machine anyway, maybe due to my typical dozens of tabs in dozens of windows... but i'd explore whether the .svg approach was the offender.
of course, lethargy won't have any impact in the course of actually presenting the thing to an audience, but there is much value to be gained by the after-the-fact mounting of a presentation on the web for later consumption by others, who will thumb through the slideshow at a much faster pace.
this is also why a presentation full of bullet-point slides, void of the accompanying speech, is not very compelling.
so even if your show does end up being a little bit slower, i think that's offset completely by your step-up in design.
I think most of the loading time is in the images, gifs and web fonts used (the svg a bit, but not so much). These days I don't see much of value in optimizing the slides for after-the-fact consumption (video is much better for that), and I just put them online so people that have actually seen the talk can go back to some of the code, links and references. And in this way I justify my lazyness for not optimizing the load time a little bit :)