Have you ever done any plugin development for REAPER? I dug into the JUICE framework for VST2/3 for a bit, and came out of that experience a little suicidal. (Kidding… mostly.)

I’ve dabbled with JUCE, and I have a couple projects in mind that I’m definitely going to do with JUCE.

JS is way easier than JUCE. It can absolutely do real-time processing.

The limitation IMO is that you’re “stuck with” REAPER’s GUI style, you can’t take advantage of external C++ libraries, and you have to have REAPER or ReaJS or some other program to compile your JS code. If you just want to write a helper plugin, get your feet wet, or target only REAPER users, JS is a fantastic place to start. Here is REAPER’s introduction to JSFX. You can probably read it in a night.

JUCE is, IMO, the “professional” option for plugin development, but happens to also be FOSS. Besides its signal processing and math abstractions, it also has a ton of stuff for generating custom GUI. If you paid for a plugin in the last 10 years, chances are it was written with JUCE. If you plan on commercializing a plugin or you just wanna go the whole hog and make it beautiful and cross platform, JUCE is the way to go. But yes, it is extremely complicated 😂.

I strongly recommend watching ADC (Audio Developer Conference) videos which are affiliated with the JUCE developers and usually offer code samples for talks where code is used. Additionally, MatKat did a free in-depth tutorial on how to write an EQ plugin with JUCE.

Beyond that, there are other choices, like RACKAFX, but IMO JUCE is the best choice unless you plan on keeping your plugins to yourself.

Actually, for plugin development, REAPER is a no-brainer IMO (even on Linux with YaBridge) for testing (other than JUCE’s plugin debugger) because it has some compatibility settings and knobs you can tweak with regard to how it sees VSTs.