As per the subject line - can these type of plugins be used in reason?
Depends on which plugin you mean, but I’ve definitely had good results with MIDI tools that generate chords. I’m using the LK MIDI controller app for Android by Imaginando, and it’s got a “Chorder” interface that will play chords, which are reflected in Renoise as MIDI notes. Similarly, my hardware keyboard has drum pads that can create chords, and those work too.
I don’t know if you’re a guitar player, but I end up doing a lot of my chordwork with Renoise’s GuttRoll pluginwhich lets you select notes on a guitar neck and translates those to the pattern editor. This allows me to transfer my knowledge of guitar chords to Renoise with ease. Highly recommended.
I also just learned the trick of holding down Shift while you enter notes, which will add them horizontally in the same track (a chord) rather than advancing the pattern editor vertically (melody). This works nicely if you know which notes go together to form a chord.
Assuming you mean Renoise, it’s not vst3 and midi channel 1 only. Then yes.