I guess the lack of response means no one here is playing on a new Mac Mini. It doesn't really matter though—the M1 chip in the Mini is identical to the one in the 13" MacBook Pro and high-end MacBook Air. So the only meaningful differences in performance would be due to the monitor you plugged into the Mini and the fact that the Air doesn't have a fan.
Interestingly, even the low-end MBA, with the 7-core GPU (instead of 8) has the same M1 chip; the difference is that Apple has deactivated the weakest GPU core. This is called "binning" and is common practice in order to salvage partly defective graphics cards, the idea being that a manufacturer can deactivate the weakest cores and sell the card as the next one down (e.g. an Nvidia 2070 becomes a 2060), rather than having to dispose of the cards entirely.
Point is, you'll see basically the same results with all M1 Macs, minus some peak performance on the high side for the cheapest Airs.
By the way, the GPU is actually an integrated chip, not a dedicated card. The M1 chip has "unified memory," equally accessible by the CPU and GPU; the GPU doesn't have 8 GB VRAM on its own. It can only access whatever RAM isn't already in use by the system, which won't be much if you get a model with 8 GB memory total.
I don't know what the theoretical upper limit is for how much memory the graphics chip can use, but the deviceconfigs I've seen all report texture memory as 5461 MB. I'm not sure Sims 3 can even use that much VRAM—we know it can't in Windows, and it couldn't in the 32-bit Mac version. If so, it would certainly be an improvement over most Intel Macs, again if the system had enough free memory for the chip to use all it wanted.
As for how the game runs, the reports are that it runs quite well overall, with some unsightly graphics glitches. The only reports of consistent crashing I've seen are from people who used their old Sims 3 user data folders or who tried to play in Isla Paradiso, which is of course still just as broken as it always has been.
The graphics glitches are an ugly pink line around the portrait UI and on some loading screens, and perhaps some blurry text, although I'm not sure that that's universal. The game otherwise runs the same as, or perhaps better than, it does on an Intel Mac with a dedicated graphics card. The various glitches reported for the 64-bit version are still present.
So overall, it looks like the M1 chip is handling Sims 3 quite well, perhaps even a bit better than the game does in its native environment. (This may also be true of Sims 4.) I'm not sure what's going on here; maybe Rosetta 2 makes the graphics processing more efficient in some way. It's certainly better than we expected going in.
