There seems to be a bit of a difference, even though both involve asking questions. To quote wiktionary:

sealioning (uncountable)
A type of trolling or harassment that consists of pursuing people with relentless requests for evidence, often tangential or previously addressed, while maintaining a pretense of civility and sincerity (“I’m just trying to have a debate”), and feigning ignorance of the subject matter, in order to wear down an opponent and incite angry responses that will discredit them.

Apparently coined by this webcomic:

JAQ off (third-person singular simple present JAQs off, present participle JAQing off, simple past and past participle JAQed off) (slang, derogatory) To ask loaded questions inviting someone to justify their views or behaviours, in an attempt to make tangential claims of little verisimilitude appear acceptable.

So the way I understand it, “JAQing off” is when you’re trying to guide your audience towards a certain conclusion without stating it outright (e.g. “Are the official numbers of holocaust victims really as solid as people claim? Are there alternative historical interpretations? I’m just asking questions here, not implying anything folks.” when you think just saying “The holocaust didn’t happen!” might make it too obvious you’re a Nazi), while sealioning is more about annoying the other party and trying to make them look bad/unreasonable and yourself polite and reasonable in comparison (e.g. “I’m just curious, is there any actual evidence that fascists are inherently bad people, as you claim? As a person with no opinion on the matter, I would just like to have an honest and open debate on this subject.” so when people reply with something like “Fuck off, fascist!” you can say “Wow, so much for the tolerant left.”). Both tactics are frequently applied by online trolls, especially of the far right, but they have somewhat different goals.

Depending on what exactly you mean, you might be onto something referred to as structural realism in the philosophy of science. Citing from the intro of the wikipedia article:

In the philosophy of science, structuralism (also known as scientific structuralism or as the structuralistic theory-concept) asserts that all aspects of reality are best understood in terms of empirical scientific constructs of entities and their relations, rather than in terms of concrete entities in themselves.

For those who want to read more, there is also an article on the SEP (Stanford Encyclopedia of Philosophy), and books like “Every Thing Must Go: Metaphysics Naturalized” by James Ladyman and Don Ross (2007) or “How is Quantum Field Theory Possible?” by Sunny Auyang (1995).

In particular, your “nothing exists” reminds me of this in “Every Thing Must Go”:

a first approximation to our metaphysics is: ‘There are no things. Structure is all there is.’