Is querying by myField=true or myField != false the same thing? Is saying myField=true better or more efficient?
If you are asking this for a search command string, then the two statements
myField = true
myField != false
is like saying
myField = "true"
myField != "false"
because Splunk does not have boolean field types, only string and number so clearly the above would not be the same.
In general, Splunk does not have the concept of a field with boolean values, as you can see from this search example
| eval x=if(true(), true(), false())