So I've been looking at various questions about the spell "Wish" on this site, and I'm seeing a lot of people respond with the list of things wish can do reliably from the player's handbook, and saying that anything else is able to be twisted by the DM.
But the player's handbook specifically says that the DM can twist wishes if they request something GREATER than the listed things. So what if something is almost definitely around the power level of these things or less, but not very similar to them?
I've seen people say that if a request is very similar to an existing spell, it's reasonable. But what if it's not? Yet is still the right power level? Can the DM still twist this kind of wish?
Also, in the case where these types of things are allowed as safe uses of wish, I have a follow-up question:
How can I tell if something's power level is in the right territory? Especially if it's not similar to an existing spell. When I look at the list of spells of a certain level, it doesn't give me a great idea of what degree of power that level represents.
I should clarify that I am asking this as a somewhat new GM. I have never run a campaign that went long enough for PCs to get to higher levels. I think there is a possibility that my current campaign will get that far (and potentially much further), so I want to be prepared on how to handle this spell.