VP9 is set up to run 2 monitors, playfield and backglass, so yup to the big 16/9 monitor for the pf, and you'll probably want a sizeable 4/3 ratio monitor for the backbox, up to you but a large one mounted 90 degrees can cover backglass art+lights and dmd pretty nicely. looking online I'd seen others have set up small solenoids to clunk with flipper button actions for a little real feel, tinted glass 3-4" over the pf monitor for some depth appearance etc.
VPforums a great place to start, they have a few programs and lots of tables you can grab and load once built.
you can built as large or small as you want, large is nice, people do nice smaller ones with less cash too.
for right now I'm just tinkering with VP8 in win98se using an older athlon 950, I'll get more ambitious sometime..