I've had multiple different interactions so far.
First one I had a thargoid link, probe, and sensor in my hold...
I immediately dropped them as a Thargoid began moving towards me with un-nerving speed.
I thne honked my disco scanner to make the probe give out it's pulse, which messed up my systems, so I was un-sure if I was being shut down by the thargoid itself. It begun scanning me, but then turned away and scanned the objects I dropped.
Then it started to collect them.
While it was collecting the link and the sensor, I managed to grab the probe, then I legged it, as a bunch of tharglets were released from the main ship and begun spinning around it.
The next time, I tried to ... hide... behind a destroyed imperial cutter hull, which slowed down the Thargoids attempts to scan me.
Once it had completed it's scan though, it turned a pretty scary shaed of red, released a bunch of thargon drones, and I began retreating backwards.
The drones gave chase shoointg me seemingly ignoring my shields, but not doing a huge amount of damage to my barely engineered Cobra Mk4.
I was able to escape pretty easily.
Another encounter the Thargoid didn't even move towards me, just picked up an occupied escape pod which was floating near a dead imperial vessel, and activated it's hyper drive. I scanned it's wake and left...
Entered another None Human Signal Source [Threat 5] to find no Thargoid at all, just several utterly crushed Federal vessels, various military items, and black boxes, and also, a Thargoid Sensor (which was nice, as a previous thargoid had taken mine in... tribute previously)
So there is some variance in what occurs for sure.