As many have pointed out, tires, wheels, and shocks can all make a signifigant difference to ride quality, especially considering the cumulative effects of those things.
However, as
@Astro14 pointed out earlier... If those changes combined don't make a big enough improvement to ride quality, you'll have spent a lot of money and end up having to sell the performance car to get a softer riding type of car (ideally a classic luxury car).
And your performance car might be more difficult to sell (or worth less money) after you made modifications that reduced performance to increase ride comfort/smoothness.
You might be better of buying a classic luxury car like a Buick Park Ave, Mercedes Benz, or other luxury car. Over the years I transitioned from Jeep Wrangler Rubicon TJ/LJ (brutal ride quality) to Cherokee XJ to Park Ave.
I modified the Wrangler Rubicon to make it ride better/softer/more comfortable. After spending too much time and money, I succeeded in getting it to ride like a normal Wrangler, which was a big improvement for my spine, but it was still hurting me too much.
So I had to sell the modified Wrangler Rubicon (losing more money in the process). The demographic who likes Rubicons and modified ones isn't seeking one with the comfort mods that I'd made. So in addition to spending money on mods, my mods also reduced resale value.
The Cherokee XJ was more comfortable when stock. I modified it to be even more comfortable than stock. It was then acceptable for ride comfort. But then my spine health deteriorated again and then the Cherokee was causing me too much back pain. I had to sell the Cherokee XJ. My mods didn't lower the value of the Cherokee, but didn't add to the value either. So I lost the signifigant cost of mods. At least it was less financially painful than the Rubicon had been.
Then I bought my Buick Park Ave and it was a huge improvement in comfort. I did suspension maintenance, two mods (shocks & swaybars) and good tire choice that improved it's comfort even more. People comment on its excellent ride quality because they're impressed (even when I haven't mentioned that it's modified slightly).
I should have bought the Park Ave in the first place.
You can give a pig a bath and put lipstick on it. It will then be a better smelling, more attractive pig, but it's still a pig. Buy an appropriate car and then if/when needed - choose good tires and shocks that will ride well. Your tire store can help you choose tires and shocks for your special needs, but that is most helpful when you have an appropriate car.
You'll get better results for less money if you buy an appropriate luxury car that already rides smooth. Whether it's a Park Avenue or a Mercedes. It doesn't have to be expensive to ride well. Though it does have to be well maintained to work properly.
