You wouldn't get close enough to be torn apart. You'd fly by and thrust into the gravity well for an Oberth effect boost. I'm thinking of unmanned probes of course. We could send them on flyby missions to other star systems to do things like take pictures of possibly habitable exoplanets. It's unlikely that humans could survive the acceleration of such a maneuver without ending up like this guy:
There wouldn't be much radiation unless the black hole were actively "eating" something, which a PBH in far solar orbit would not. That's part of what makes it hard to find and what makes PBHs candidates for dark matter: they're dark and don't do much unless something encounters them. There would be no net emission of Hawking radiation since the BH's Hawking temperature would be colder than the cosmic microwave background.
The hypothetical PBH that could be planet 9 would be about 2-3 Earth masses and about the size of a golf ball in terms of event horizon radius. You couldn't get that close to it without being "spaghettified" and added to its mass.
Probably the most valuable thing we could do with it is study it and use it as a lab to learn about quantum gravity. We could chuck small things into it with probes nearby to precisely measure the result, etc. All black holes we know about are far too distant to reach. Having one we could study would be huge.
