[HELP] Is it worth to update to VapourSynth R55 or R56?

[Selur]

Why two versions of VapourSynth where released?

R56 is the newer version and contains some bug fixes regarding the new APIv4.
R55 is also available as a APIv3 build at least on Windows.

Will those VapourSynth versions work with Hybrid as is?

No.

Will those VapourSynth versions work with all current plug-ins?

I think normal filtes will work, vsViewer not. (needs a complete rewrite)

Are those VapourSynth versions supported on macOS Mojave?

Can't say.

From Hybrid usage point of view - is it make any sense to update to R55 & R56?

R55 is uninteressting unless you are on Windows, there the APIv3 version works.
Mainly R56 brings a bit better memory management and some speedups for some and some slow downs in other versions.
Since Hybrids Vapoursynth preview will not work with R55 and newer unless AVI3 is used, you would lose preview support.
So I would not recommend switching to it atm.

Cu Selur