-Were there steps on the back of the Argentine prop?
Yes, steps behind the prop. They actually do a bit of a drumroll buildup for the contestant climbing up and appearing at the top of the board.
-The 2001 France paint job makes the set look more like a pinball machine than anything else.
It's funny you mention that, given that the French 2009-2015 series literally introduced a pinball version of Plinko called Le Flipper:
-What were they trying to accomplish with the 2009 France design? At least straighten the set. Then maybe it won't look as bad.
It certainly had its problems:
Two bonus images of the board from the contestant's perspective, and the host literally climbing to the top to dislodge a chip that was stuck.
-Italy: It looks like the hostess is opening a door of some sort. Brosa, can you provide any insight on this?
In this version, the middle is a 0. However, if the contestant won at least 2 million lire and still had at least one chip remaining, the 0 space became an "AUTO" space to win a car. To win the car, they'd have to give up any cash and hope the chip landed in the AUTO space, otherwise they'd lose everything.
Also, here is Italy's version from the early 90s which I missed:
-Apparently, Mexico also had a Plinko turntable prop, at least until 1997.
Nice pickup!
-The Romanian Plinko has some long pegs. Brosa, was this played with balls instead of chips?
I only found a couple promo shots of the Romanian series (Plinko is the only game I have of theirs), but given how similar it is to the French 09 series I'm guessing they used chips (balls would surely bounce off the curved part?)