Is there any way to disable the invincibility of the "Data Disc" and "Psi Emitter" powerups?
Using set invincibility does not seem to work. You can assign it hp just like any other powerup, but these particular ones are invincible.

Thanks for reading

No, they can't be killed. Ever.

Gas tanks/minerals can be killed, and those are the only ones, and the reason that the hallucination powerup glitch works. They are also unplaceable in staredit. That being said, no powerup you can create with triggers can be killed.

What is the hallucination power glitch? And you can place them in scmdraft

The glitch only work in game but they can be placed in the editor. When you try to pick up whatever the power ups turned into, it becomes a unit, building, rubble, or sprite that your builder can carry. I think someone has a list of what turns into what.

???
I tried picking up every hallucinated powerup and they all just turned into regular powerups.

http://www.maplantis.org/index.php?topic=2997

It is not having that effect for me, the hallucinated powerup just turns into a regular powerup when you pick it up and never expires.

It looks like it never expires, but if you wait like 2 minutes, then kill that worker without building anything, the game will crash, since the worker is trying to drop a missing powerup, and no unit has been created to replace it.

Is there a way of creating the resource things such as Vespene Orb, Vespene Tank, Mineral Chunk etc?
Either with triggers or by some other method (besides preplacing)?

No.

That only happens for some units. You can still get another worker to pick it up again, but it might be harder, so you have to get it ontop of a burrowed unit and unburrow.

What do you need it for ? Maybe one can think about another way to do what you want. All roads lead to Rome.