How would you handle "as if with clairvoyance" and "as with the spell scrying" for magic items?

[Senko]

I was doing some research on whether magical items like crystal balls could see into other planes of existence and I noticed something in the description for mirror of mental prowess and crystal ball descriptions. Specifically the mirror is stated to work like clairvoyance while the crystal ball is said to work like scrying. So my understanding of this would mean the mirror can scry anywhere (if your familiar with it?) buut can't be used to find individuals while a crystal ball can only view individuals not locations. Am I reading this right and if not how would you handle it?

[Pizza Lord]

In the case of the crystal ball, it views a creature. You may be able to get some details of the immediate area around it (maybe 5 feet or so, maybe more), but it shouldn't be really focusable, you might be able to read big letters or symbols, but probably not a book or some regular letters unless maybe they were holding or reading it.

It functions as scrying, so presumably the target will get a Will save and there's a table with modifiers for the spell, but it also specifies that creatures on a different plane get an additional +5 modifier to the save in addition to any other modifiers.

The mirror of mental prowess functions as clairvoyance and effectively creates a magical sensor at a locale or location (which is known to you). It would allow you to observe any creatures in the area, but it doesn't target or find them unless they wander into the location you're spying on.

Normally, clairvoyance (and clairaudience) do not function across planes (as stated in the last line of the spell), but the mirror itself specifies:

Mirror of Mental Prowess wrote:

View other places as if with clairvoyance, and the controller can even view locations on other planes if she is sufficiently familiar with them.

TL/DR

You are correct. Scrying=Creatures. Clairvoyance=locations. Both items work across planes.

[Diego Rossi]

Pizza Lord wrote:

TL/DR

You are correct. Scrying=Creatures. Clairvoyance=locations. Both items work across planes.

All correct. I want to add a note: with the Mirror you see a location, but if in that location there are people under the protection of Mind Blank you are still unable to see them.

[Senko]

Still seems like you would want both of them if you can afford it, the crystal ball to find creatures and the mirror to view locations/travel to them plus its other functions. I didn't realize they were this different.

I haven't seen any tables on familiarity so I think its a GM call on whether someone is familiar with something or not. Personally I'd be inclined to do something with the teleport table studied carefully, either a place you've been often (but don't feel at home like very familiar) or have a focus of some sort (map, picture, etc) on hand. Maybe even a very detailed description in a book.