PlexiGlass is an inaccurate term and 90% of the time refers to thicker grades of acrylic.
Acrylic is made for window treatments where image clarity is more important than impact resistance. It's also used where abrasion resistance is very import, such as display cases. Therefore it is used for green houses and some types of triple layer energy efficient windows. It's not that great for tooling simply because it melts easily (at which time it may give of toxic fumes, I know because it gave me the worst headache I've ever had).
The same easily meltable properly allows it to be thermally warped at lower temperatures than polycarbonate. But this should be attempted outside of a professional level or controlled circumstances because it is EXTREMELY dangerous to heat acrylic.
Lexan (Polycarbonate) is made for impact resistance but is much easier to tool because of it's low abrasion resistance. I highly prefer it because it won't give me brain damage if I accidentally melt it while cutting. It flexes without cracking too.
As far are cutting, abrasive discs will melt either material unless ou use the lowest speed possible.
I recommend using a jigsaw and a metal-smooth cut blade to get the best edges on your cuts. And you have to go as slow as you can to avoid melting the two piece back together. BUT LEAVE THE STATIC PAPER ON. Both materials can get scratched from tooling so the protective sheeting needs to do it's job.
McMaster.com sells Acrylic and Lexan in a variety of shapes, thicknesses, sizes, colors and tints for comparably good prices. (as versus Home Depot or Lowes which only stock building code standard sized sheets at 1/8" thickness).