I honestly just find it most annoying when someone has knowledge from another world and that somehow makes them super OP with magic. If they are at normal strength or stronger than normal for reasons that have nothing to do with being from another world, I'm fine with it. But OP due to transport has always felt like lazy writing to me.
I agree that it's unrealistic with using knowledge cause I know of an airplane but that doesn't mean I know how it works or the physic behind it. The thing is what's OP about a transported character is their different mind frame and thinking pattern. The locals have one thinking pattern and the character has a new one.
Think I'll stand on the other side for arguments sake xD
I would argue that while the knowledge from earth shouldn't make a person instantly powerful, applying that knowledge would give related magical fields a large boost to their output.
Let's take fire for example. We know that fire burns hotter by introducing higher quantities of oxygen. We also know that introducing the fuels in different states with change how the flames react to it. So if a mage could apply that knowledge to their fire spells, they can imitate anything from a fuel-air explosive, to napalm.
We can do the same for air via by tampering with the quantities of the different air particles(oxygen, carbonate dioxide, helium, ect ect), raising or lowering the air pressure, or using vibration to create walls of sound.
Water, purity for clarity and hardness. Viscosity, salinity and particle movement to either freeze or boil the water as needed.
Hell even the basics of gravitational forces are covered in highschool...
So I would argue it's not that we have overpowering abilities in another world setting, it's the application of our knowledge that twists and augments whatever abilities we are given