Yes, the model is of course distinct. If it were the same, then Model A and Model B would be one and the same model and this exercise futile.

Allow me to present first the inner working of planet Earth in light of gravity before moving toward the larger structure. I am sure this view is not a standard view, though I know that some physicists do agree on this.

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The center of planet Earth has a net-zero gravity point in the exact center. It means that the entire mass of the Earth is pulling on that center, except for matter exactly in the center because all is in balance at that spot.

When standing on the surface of the planet, the entire planet is pulling us down, gravitationally.

When standing halfway inside the Earth, all matter above will pull in the opposite direction from, say, three-quarters of the planet found underneath and to the sides of that position.

I am going to flatten this image now to a clock.

At 2 o'clock, matter is pulled toward the center by all matter found in the large area between 4 o'clock and 12 o'clock. Matter found just in the smaller area between 12 o'clock and 4 o'clock will pull sideways -at best- on matter found at 2 o'clock. Collectively, gravity pulls matter at 2 o'clock toward the center.

Notice that gravity pulls across the center on matter of the other side.

The 'fun' part is that specific matter at each hour on the clock is pulled by about 8 hours of oppositional matter (between 4 and 12 o'clock for matter at 2 o'clock). A collective pull is then discovered on specific matter therefore.

The individual parts of matter on planet Earth are of course not individual parts at all; they are part of the whole planet. Yet specific sections of matter are pulled by the entire remainder of matter, each in various directions, depending on where the specific section of matter is located on the planet.

So your last words of your reply are correct in that a collective across the galactic center (meaning something like two-thirds or three-quarters of a galaxy) is pulling on a specific star or planet found in opposition to that large collective of stars and planets.

As such, we will always have a formidable collective force that pulls on all stars and planets. What that exact collective force is based on depends on the location of the one star or planet we are talking about.

Our Sun (or the Solar System) is pulled by the entire Milky Way, much of it from across the Milky Way’s center. Our Solar System is pulled by a different section of the Milky Way than a star system in another location of the Milky Way (but there can be much overlap).

Yes, I am simplifying things. Gravity is just one of the important players to declare how a galaxy ends up structuring itself. It is a lot more chaotic than what can be written down in words.

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In Model A, we see a replication of the Solar System in which the heaviest object is 'found' in the center.

In Model B, the Galactic structure is nothing like a 'simple' star system. The collective pulls, and it pulls any which way it can. The spot in the center has the strongest gravitational depression imaginable.

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When discussing cities and city centers, something similar can be seen.

Starting out with a downtown in a small place, we can see certain functions in that downtown.

With a larger city, we see more functions in the downtown area.

With an enormous city like New York, we see a downtown area with functions maximized into super skyscrapers.

And yet, there is a fourth model: the Realm model.

Instead of having a super downtown area (still nothing to sneeze at), Los Angeles has all its functions strewn about. Folks can live in the greater LA area and hardly ever make it to downtown. Their work is not in downtown, they don't live in downtown, their entertainment and restaurants are not in downtown.

That fourth model does have a downtown in Los Angeles, and actually increased a bit in importance but only because LA started to have a (more) serious transit system and because LA business recognized that certain economic benefits can be had when there is a functioning downtown.

What Covid showed us is that we actually don't even need a downtown, as long as we can get the job done and find our entertainment not too far away from home.

Sorry, had to add an analogy to this, Rex.

I hope you see there can be a Model B. We just need to figure out how much less mass there would be in Model B compared to Model A. As far as I can tell, this may make a small difference though found at the astronomical level, enough to warrant further investigation.