I've heard they average out at Solar System Level, but other than that there's nothing much we can really do for it.

Plus the Real World verse serves as a reference for feats in fiction, for feats like killing lions or destroying tanks. And it goes without saying that the way fiction portrays black holes is often inaccurate.

and in their verses, they cannot be escaped once you get too close

so anything made of matter or a part of space-time in general will be destroyed unless they have a super special hax or are non corpeal and not a part of space-time

However I recall we could use ths size of a real life blackhole as don't they tend to vary from Solar System to Multi Solar System level? From normal sized black holes to supermassive black holes.

Well, given that they seem to destroy anything whatsoever that is a part of 11-dimensional spacetime, I do not think that they can be properly quantified.

^ It is a hypothetical situation as how the crap could you destroy a actual black hole as creating a black hole came from a supermassive star with its gravity increased and collapsing the star itself to make a black hole.

The simplest static black holes have mass but neither electric charge nor angular momentum. These black holes are often referred to as Schwarzschild black holes after Karl Schwarzschild who discovered this solution in 1916.[12] According to Birkhoff's theorem, it is the only vacuum solution that is spherically symmetric.[45] This means that there is no observable difference between the gravitational field of such a black hole and that of any other spherical object of the same mass. The popular notion of a black hole "sucking in everything" in its surroundings is therefore only correct near a black hole's horizon; far away, the external gravitational field is identical to that of any other body of the same mass.

Solutions describing more general black holes also exist. Non-rotating charged black holes are described by the Reissner–Nordström metric, while the Kerr metric describes a non-charged rotating black hole. The most general stationary black hole solution known is the Kerr–Newman metric, which describes a black hole with both charge and angular momentum.[47]

While the mass of a black hole can take any positive value, the charge and angular momentum are constrained by the mass. In Planck units, the total electric charge Q and the total angular momentum J are expected to satisfy for a black hole of mass M. Black holes satisfying this inequality are called extremal. Solutions of Einstein's equations that violate this inequality exist, but they do not possess an event horizon. These solutions have so-called naked singularities that can be observed from the outside, and hence are deemed unphysical. The cosmic censorship hypothesis rules out the formation of such singularities, when they are created through the gravitational collapse of realistic matter.This is supported by numerical simulations.

The Living Tribunal1 wrote: the thing is, no matter how many dimensions there are, a real black hole infinitely stretches all of them within itself

Where does that idea come from? Doesn't a black hole usually just deform spacetime (or 11-D spacetime assuming supergravitation)?

A black hole deforms the space-time system it is in

if the system has 2 dimensions of space and one of time then all of them get deformed

same goes for 3-spatial and 11 spatial dimensional cases

what happens in a black hole is space-time gets stretched near infinitely to its singularity (hence the time dilation and the spatial stretching once you enter into it)