Different behavior for a VI from lvlibp.

[CoastalMaineBird]

One with an event structure and one with dequeue element. Can some of them block the UI thread?

The EVENT structure, by definition, means "Wait for something to happen". It does NOT block anything.  I have an app with upwards of 100 EVENT structures, all waiting at the same time. No problems.

I don't know the innards, but the DEQUEUE ELEMENT is also very cooperative - if you give it a timeout, then it waits without blocking anything. 

[CoastalMaineBird]

I should clarify that an EVENT structure will not block WHILE WAITING FOR AN EVENT.

WITHIN each event case, there is a LOCK PANEL option, which means it will ignore front panel things WHILE THAT CASE IS EXECUTING. By default, that option is ON, that's what you want in 99.999% of cases.