I set the anti popup slider to 20, and when I was landing the buildings still poped up around a 1 mile final. Any suggestions?
If by "buildings", you mean the main terminals, these are not handled by that slider, and are not even using dynamic loading range so, they are always loaded when in the scenery range, which is 8 nm for PHNL so, it's just not possible they would load at 1 nm.
Don't confuse buildings, with additional extra detail on them, which is the LOD in action.
For example, a building might load at 8 nm, but a more detailed version of it will load closer. This doesn't have anything to do with the Anti-popup and, since it's NOT causing pauses (because the object is loaded entirely with all its LODs only once), will stay like this.
The things that are controlled by the Anti-popup slider are smaller details, like ground vehicles, cars, signs, 3d taxilghts, etc..