WISP nose mask vs. nasal pillow, mouth breathing

Been at this a couple of weeks and still learning/suffering... Started off with nasal pillows, but sore and nose, as side sleeper. Trying WISP, which I like. Best with large size, even with my medium schnoz. Many adjustments and clip off nose tube, lets me breath when I get up in the middle of the night to let me or the dog go to the bathroom:-)
My concern is that with the nasal pillows I knew when my mouth was open, since the air was rushing out, and I could train my tongue to rise and block the air, at least when awake, and hopefully when asleep. With WISP, I don't feel much air rushing when mouth open, and can confortably keep mouth open. Not sure why, as both force air through nose. The chin strap, Apria's only one, which they call premium, doesn't always keep closed mouth, and in any event I liked the tongue doing the job.

I had the same problem and the chin strap I got from Apria helps enough to keep my leaks in check most of the time.
I got the impression that the girl I talked to at Apria did no much about chin straps, but could choose from more than one to order from. I wasn't sure if I knew twice as much or half as much (2 X 0).