[MrTracey]

I had a 24hr loan of an X1 Xdrive20d M-sport with the 19" wheels +run-flats.
The dealer asked me what I thought of it. "Terrible" I replied. Harsh ride & bad road-noise.

I didn't have any say in the spec of the loan car, but I already knew that combination of wheels/tyres/suspension was one to avoid on anything other than smooth new roads.

I've ordered an X1 (20i) in M-sport spec - but with 18" wheels with non run-flat tyres and EDC. I've not driven one in that spec, so I'm taking a leap in the dark but it has to be better than 19"/Run-flat/M-sport suspsension.

About 6 years ago I had a 120i M-sport with 18" wheels & run-flats. It was like driving a go-kart. Changing the tyres to non run-flat made the car just about bearable. I swore I'd never have plain M-sport suspension again.

So, my advice -
I don't think just changing the tyres to non run-flats will be enough as they will still be quite low profile on 19" wheels. So the minimum would be a change to 18" wheels and non run-flats.
However, there are also many, many unfavourable reviews of the standard seats too. So it looks like your option 4 or 5 is the only way to go.

Can you arrange a test drive with that combination? Will the dealer put a set of 18" non RFTs on your car for you for a day?

If you choose to change the car, then next time read/watch as many reviews as possible. The issues you identify are widely reported.