Before i send my old audio interface to someone else, i do some tear down and cleaning as final goodbye, as i do some probing with oscilloscope, the thing that surprise me about old converter (in this case is Steinberg UR22) it's pretty clean even maximum sampling rate at 216kHz, the pre amp is a little noisy, still performing perfectly considering how old it is (Jan 2013). The unit itself say capable 192kHz but the chip itself have some Sampling "headroom" up to 216kHz. So, i think most interface people have these day is more than good enough, so you have nothing to worry about.
Portamento timing is... self explanatory: they control the timing of the pitch changing between note, faster or slower(lag) than default(64)
Opening: is control the mouth opening the default value is max(127) singing with clear tone, a lower value create an less distinct tone, good combination with Accent param*
Clearness: is more like a white noise, give some brittle sound.. very eardrums torture if push too high, a little amount with low brightness can create an fragile voice
Breathness: i don't really use it but it give some air to every word in a very small amount
Brightness: this is interesting, and very useful it can use as volume control and tension control, high value make it loud and in your face sound, lower value make muffled sound and feel mellow-ish laid back voice, work great as overall volume control.