The $esxcli object is not you ordinary object, the "methods" are all codeproperties and/or codemethods.
The easiest way to see all calls that are available is to do
$esxcli.esxcli.command.list()
I'm not sure what you mean by the 2nd part of your question.
What do you have in the $satp variable ?
If you want to see all devices, why don't you just leave out the Where-clause ?