I tested synced variable syncMode with float variable. "linear" syncMode don't work well. It has jitters. "smooth" seems to be completely broken.
Environment: UDONSDK-2020.02.28.21.02
Details:
I used two VRChat clients on a PC and captured windows together. Right side is the owner that does SetVariable 0 and 10 periodically with 1sec interval. Each ball visualizes float variable. Green one shows "none" syncMode variable. Red shows "linear". Blue shows "smooth". Also you can see values as formatted string above. Left side client receives synced value and shows values as same way. I unchecked "Synchronize Animation", "Synchronize Position", "Allow Ownership Transfer on Collision" settings on UdonBehaviour component.
Results was
* Green "none" works fine.
* Red "linear" moves between expected range. But it has jitters. Jumping to middle of the range is also unexpected behavior for me.
* Blue "smooth" goes away. -3.40282347E+38 is Single.MinValue.
When "Synchronize Position" is checked. Synchronization stops after about 5sec on non-owner side. See this: https://twitter.com/naqtn/status/1234124333800255489
(Also in this movie, at the moment just after joining, "linear" case value becomes out of expected range. you can see -12.40506.)