It is important the remember that 3D printing prints upwards and anything printed requires something underneath it or it will fall.
Supports are required when otherwise you will be printing in the air.
There are many different settings for supports and different types of support.
Using supports just from the build-plate vs on the model can increase/decrease the quality.
You should consider exploring support interface layers. This is where you use a different type of filament immediately underneath the area requiring support. It requires an AMS, but, it requires significantly less filament swaps as it is only used on the layer immediately below the supported layer.
PETG is a support material for PLA and in reverse for example.
For that model I think the easiest thing to do would be to split it into two halves and then lay them on their backs. The columns would need to bridge - so might be slightly untidy at the back - but I guess you could print them separately and slide them in.
Would probably add something like a ‘springy t joint’ or double sided dovetail to fit the two parts back together.
If you do need to print them in the orientation presented - then I tend to add my own supports in the CAD model - trying a few iterations until the underside of the overhangs look ok.
One way you could achieve the perfect finish is the print the balconies as separate parts with plugs on the inside edge with matching sockets in the face of the main building.
You then insert each balcony into its position with the plugs inserting into the socket hooks, possibly with a dan of glue.
The plug/sockets are just cylinders placed horizontally one at each end and another in the centre with the sockets as holes in the model.
Make the socket 0.2 to 0.4mm bigger in diameter (experiment) and at least 5-10mm.
Think of an electrical plug and wall socket.
This way your balconies require no supports.
The balconies with columns could have the columns printed separately with a small notch in the top and bottom of each balcony to accept the cylinders in, a drop of glue to secure them.
What I mostly do is just create little columns in Fusion 360 - either straight or angled - and then pattern copy them along the overhangs - then snip them off if necessary - although I have considered adding some sort of tab on them so that they can be twisted off.
I think you should be able to get joints less visible than that when bringing together joints that have both been printed horizontally - as you should be able to get nice square corners - you then just need to pull the parts together tightly - with bolts or springy T Joints (also from Slant3d). If your main body was printed vertically then it will have slightly rounded corners which are much more difficult to hide.
I suppose you could print all of the balconies separately and just slot them into the main body as another option.
I’m not sure what your expectation of the technology is but if you are expecting museum quality props off the printer bed, that’s a bit much to ask with the technology so far.
I would suggest any other filament that Matte but particularly Bambu Matte. It is by far the worst performing Matte filament I’ve used and the factory settings are so far off, you really need to perform manual calibration. I’d suggest Overture or anything other than Bambu.
If your going to do client-facing models, reset your expectations a bit you can get here but you’ll have to do some post processing. I’d suggest starting off with a dark grey and then spray painting it with a good primer and then your final color. It’s important to start out with as good a print as you can get.
I did take your 3MF file though and looked at it. The 0.2 nozzle is clearly working against you and the Bambu filament is only making it worse.
Although I did not print your entire model, I cut out sections of it and printed a representative assembly. I’ll go into what I noticed but here are the photos.
