can I suggest something to you.
Learn to use an internet search engine.

Most of the smooth models you see are produced either by sls on powdered nylon or sla with resins. No comparison to fdm, appearance wise.

Also pretty much every question you ask can be easily answered by a short internet search.

Is there currently much selection in nozzle diameter for consumer devices? Does it make sense to change between arbitrary diameter eg. via a quick change system like on newer Ultimakers? I mean would there be issues with filament feeding or other parts of the moving print head - obviously travel speeds etc could be an issue with fine&fast printing if the printer is not designed and built with that in mind.
So an internet search would tell you that:
yes, lots of available nozzles.
Quick change systems are good
The slicer handles most of the changes - as long as you tell it the nozzle diameter.