First, you do NOT want THREE separate pieces of glass or anything else between two areas - it's mass-air-mass that gives best sound isolation. The only reason to angle a glass is for visual reflection control (glare) and mid-high (sound) reflection control. For both, angling the glass to reflect downward and then putting absorption across the front of the mix desk (toward the window) works well.
The downside of angled glass is that you lessen the distance between inner and outer glass, which can reduce low frequency isolation. Using THREE pieces of glass will VERY NOTICEABLY reduce your low frequency isolation - believe it or not, but leaving one piece OUT of your window will actually HELP rather than hurt.
If your window is part of a true double-framed wall, then the glasses should go close to the same plane as your wallboard layers (as far apart as possible) and you'll improve isolation somewhat by allowing the window cavity to "breathe" into the wall cavity around the window.
If you make sure both pieces of glass are clean and dry before installing and sealing, and you vent the cavity as above, then as long as both rooms are kept at or near the same temperature there will be nothing to condense.
As an "insurance policy", you can install one of the glasses using soft rubber and cleats held in place by screws with finish washers - then, if your situation causes condensation you can easily remove the glass for cleaning, and then add some small bags of silica gel between the glasses -
HTH... Steve
Oh, forgot to mention - glass is roughly 3.5 times as dense as gypsum wallboard, so your 1/4" pieces will almost keep up with two layers of 1/2" wallboard each side of the wall.
