Other than going monochrome and no sound, what do you notice about silent movies?
Typically the speed isn’t consistent as the film cameras were much cruder back then…the highlights tend to be a little blown out in many of the clips we see today, though whether that was the case when the film was actually shot is a different story. Contrast was the name f the game…backgrounds tended to be dark as the lighting necessary to get an image was substantial and if it was shot on a soundstage, the main characters seemed like they were the emphasis light-wise in many cases.
There’s no plugin that does this AFAIK. However, the effects generated by the most observant of us tend to surpass what you can do “out of a can” anyway.
I have just started creating a similar project, and found that a good effect is to use a number of keyframes to change the ‘Fast Blur’ blurriness settings from zero to around 10-20 and then back again.
Combining this with changing the zoom level of your footage and/or intertitles by using keyframes on concurrent frames from 100% to 99.5%, then 100.5%, then back to 100%.
This will give the impression of the traditional ‘jumpy’ look that goes slightly in and out of focus every now and then.
using the Sepia overlay and altering the contrast settings, as well as possibly adding some ‘dust and scratches’ should give you that authentic early 1900’s Charlie Chaplin/Buster Keaton Silent Movie effect.