So I managed to arrange a last minute test drive at 7.30pm last night and I currently have a White MYLR on 19's on order. I currently drive a current model Audi Q7 with air suspension, like others I was worried about all the reviews online talking about a harsh ride on 20's. I arrived early so had the car from 7-7.45pm and both my wife and I drove the car. On smooth surfaces I had no issues with the 20's whatsoever, so the dual carriageway outside and around Thorpe park were perfectly fine, on slightly bumpier surfaces and riding over cats eyes there was a jiggle but nothing that was a show stopper, I suspect on really bad surfaces it could be a little unsettling and not as well absorbed as my Audi, however the handling characteristics are great and I found it to be very responsive and sharp. My other car is a E63 AMG so I have some experience in order to make a comparison. Getting back in to the Audi Q7 afterwards made it feel more boat like even when put in its firmer dynamic setting. So I'd say its a trade off, if you are an enthusiastic driver and like a decent handling car then you should have no issue with the Model Y's suspension set up, I suspect the 19's will offer a marginal improvement over the 20's however I don't think its going to be a night and day comparison. I've instructed Tesla whilst at the demo centre last night to change my order to the 20's based on my experience as I prefer them cosmetically over the 19's. I have seen some video's on Youtube and the Tesla rep's also mentioned that you can take off the gemini covers and either paint them with a black plasitdip spray or the alloys underneath and get the best of both worlds if you don't like the silver. From my research the gemini wheel covers only offer you better range whilst at motorway speeds and less so around town so unless you do a lot of long commuting you may not see a lot of range improvement over the 20's or the 19's with the wheel covers off driving locally.
In terms of sound insulation, we had some vibration in the rear, when I pulled over and swapped over to my wife driving we noticed the middle rear seat was down and folded over but not clicked in so we just put in back to its upright position and the noise issue was gone. We drove mostly with the radio off to get a good feel for the insulation levels and again coming from the Audi I found it fine. I cannot confirm if this would be the same at constant motorway speeds but I didn't notice anything to put me off.
Only negative I can see was the rear view visibility out of the back window was like looking through a letter box but once you get use to the on board cameras it should be less of an issue.
Hope that helps.
T.