Circuit:
A VCO + simple 2-stage opamp that feeds the VCO comprise my entire circuit.  Also, a feedback path is taken from the VCO back to the opamp.
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Question:
Now, which method is the appropriate one to find out the stability of the opamp loop using iprobe component  -  tran+stb  or  pss+pstb ?

Is it tran+stb because its an opamp loop? or is it pss+pstb because there is an oscillator?
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Since I'm unsure, I curiously tried simulating with both methods.
The loop gain plots seem totally different and so do the corresponding gain and phase margins!  For e.g: the loop gain magnitude for pss+pstb almost always starts from close to 0 dB and rises midway around, irrespective of the opamp open loop gain.

Could anyone kindly suggest the right analysis that suits this task?

You would use pss+pstb because the effective operating point is periodically varying. With tran+stb you effectively freeze the oscillator at a certain point in its limit cycle, which would give the wrong result.

-Ken