Which plist are you referring to? It’s true that OmniFocus maintains a lot of its display preferences using the system preferences daemon (
cfprefsd), which uses plists to store preferences as an implementation detail. It’s generally unsafe to just copy those plists around, though – the preferences daemon on each machine may not notice the plist change, and might actually overwrite your updated settings with old ones or behave otherwise unpredictably.
Unfortunately, I think the safest way to keep preferences in sync is to do it manually on each machine. You’re welcome to request that particular settings be synced, though – send us an email!