I have an RS rear sway bar, the stock front sway bar, 21mm front torsion bars and 27mm rear torsion bars with Elephant Racing poly bronze bushings all around. I love the car exactly as it is. I had it corner balanced and aligned by a race shop; worth every penny.
The most important part of my suspension system was the digressively-valved, matched & calibrated shocks from ER: after 500 miles of bedding in, they were absolutely perfect. They offer compliance over bumps and taut handling in corners. Expensive, but stupendous. They were paired to each other and adjusted for my torsion bar choices.
Regardless of how stiff you choose to go on the torsion bars, I strongly recommend that you have your shocks matched to each other and tuned to match your torsion bars.
https://www.elephantracing.com/porsche/911/component-services-for-911/shock-services-and-testing/?srsltid=AfmBOorzEvLw7JEhuZ417Fna6XAN34fyZhl9X9quV EomNYck9qJokYBu