If you're interested in using Audio Plugins via a USB loopback (I do this when a little bit of latency isn't too much of a problem), these 2 plugins are good:
https://kilohearts.com/products/formant_filter
https://whiteelephantaudio.com/plugins/songbird
For midi:
https://shop.fkfxaudio.com/b/sylab
https://www.audiothing.net/effects/the-orb/