Do Turntables sound better with time?

I have never observed that. Doesn’t mean it doesn’t happen… but if it does it is pretty subtle.

The turntable is more likely to be a constant. The phono cartridge is likely to improve with playing time as the suspension of the cantilever loosens up.  I suppose it's possible that the preamp or amp were "burning in" and improving with time, if they were new.  

NO.  Maybe the cartridge, but in my experience (55 years since my 1st turntable) a turntable will not change, unless it starts to breakdown. As noted above, other factors may improve the sound.

Any audible difference would be minimal but we have ta accept the fact that for a new set up many things would change with use. Bearing, motor, power supply, tonearm cabling, let alone cartridge. Can we isolate any change individually?

Most all mechanical things have a break in period. You did not state if you are using the built in phono preamp but that would be another item to consider.

How audible are these factors? All depends but seems no reason to doubt what you have noted.