If you're interested in creating time dilation, then a planetary mass black hole unfortunately won't get you any further than, well, a regular planet with the same mass.

(Aside: time dilation already occurs on and around Earth. GPS satellites have to account for the fact that time runs ever so slightly slower on the ground.)

So, it’s not the local strength of the gravitational field, but the overall mass that matters? How does that work? I mean, if distance/ intensity doesn’t matter, than distance is irrelevant? That seems extremely counterintuitive.

I thought that since you could get into areas where the field was arbitrarily intense, that it would be able to provoke significant relativistic effects.

I had assumed that the small mass would make tidal forces more problematic than with a larger one, but if the distance/intensity of the field isn’t a factor, but only the overall mass… wouldn’t that mean that we could utilize black holes at arbitrarily long distance to provoke those effects, so it would just be a universal constant based on the mass of the universe, and there would be no relativistic effects on a relative basis?

What am I missing here?

I don't think that's right except at a radius of a typical planet. At the event horizon of even a planetary mass black hole, gravity is so strong that light cant escape, and the time dilation effect should be the same as for any event horizon.

Not really, the max acceleration/gravity you can get from earth is around 1G. Even if you tunneled to the center of the earth, you'd get ... zero g.

However with an earth max black hole you could get closer, which would have a higher acceleration, and would time dilate more strongly.