If you like this sort of thing you may enjoy Phil Lapsleys book Exploding the Phone which is also available in audio book format.
Jason Scott also had a section of Textfiles.com dedicated to similar content with actual recordings of conferences, early streaming audio shows, vintage recordings, etc.
At least half of it is at http://mixlr.com/prankcallnation/showreel/
Usually they put up a torrent of the whole thing, but nobody's asked me for my audio yet, so maybe they aren't going to. Or maybe they haven't asked because it's already on the Mixlr.
TextNow is pretty good. It's available on windows, android and ios. As to the speech distortion aspect, there's lots of free software that'll let you do that (Clownfish Voice Changer is one of the most popular ones).
I think in the $650 range. The SDS100 is a pain though. Too complicated. For a hobbyist the 436 is top of the line, good for 99% of everything you'd want to do.
https://www.amazon.com/Uniden-HomePatrol-TrunkTracker-Programming-Emergency/dp/B08JHDGLL1/