…what happens? Does it work? Do plugins get substituted with their 64-bit counterparts if available?
Or is this just going to crash the project? Curious.
Crash, blows up, kabooooom, bzzzzzzst?
LOL… just guessing 
Hmmmmm… Something could really happen… with UAD Plugins
Specifically, this post in that thread:
Mh, gooood question… Regarding offline plugins… I would say if you click “modify” it will open just the 64 bit version…
Why not check it out? Clean project in 32 bit, one track, freeze - close, open in 64bit?