Swaybar stiffness. Such thing as too stiff?
 

Your car is setup for a lot of understeer. If you don't feel it your not going fast enough.

At some point you will lose compliance and lift tires off the ground, which is obviously not good for traction. The reason for the stiff front bar normally used on the s2000 is to counteract rear wheel lift and to make the vehicle handle more neutral with a square setup. This is something that the AutoX people use because the B/C street category only allows changing of one bar. People change to the softer Miata bars to combat snap oversteer and again with a square setup would help to make the car more neutral again. You have added front grip by going square and this would cause the car to oversteer worse. I have the Karcepts .25 bar and started on max and really wondered what the heck was up with how badly it handled. It horribly understeered, so I would just throw it into the corners to get rotation and would just end up spinning out. I want to get the Karcepts rear bar to soften it, so I could also soften the front a bit more. Currently have it on the middle setting and seems to handle great now!

Going square induces far more understeer than stock. Therefore, you want to stiffen the front and soften the rear. You have done so with the front bar. Now, change the rear bar to an '04 or later, and you'll notice the handling shift towards neutral immediately.

You didn't say where. On the street? At track days? In Autocrosses? Each has different criteria.

For example, competitive competition classes have rules, where w2w or not. Street autocross classes can't lower the car, must use OEM springs, can't use offset ball joints limiting front camber to -1.9°. STR limits rims to 9" width, tires to 255. Can't use metal bushings. The negative camber that would be optimal on track would cause excessive tread wear on the street.

For track cars, that is often the most important criteria with enough other cars running to establish what is the best practice.

For street cars, a driver will never be at continuous maximum lateral forces. First, there are few street turns tight enough and fast enough to be at the limit. Second, if you are at the limit all the time, eventually you go past it, with really bad outcomes on the street. Third, on the street there are oncoming cars, pedestrians, police, and the assumption you stay in your own lane. So feel is much more important. The Mazda Miata is widely praised but runs on narrow tires with a fairly soft suspension.

That stiff front bar makes it seem more responsive on the street from my personal experience.

On the track, the combination of springs, bars, and shocks will depend on the track surface, the track shape, speeds involved, and aerodynamics. Generally less stiff adds more mechanical grip and more aero needs stiffer springs. With the short wheelbase, many have found they went to stiffer springs to control pitch (e.g. brake dive) and roll, requiring less from the anti-roll bars.

If you search the threads here you will find cars running competitively in SCCA E/Production and T3, and NASA TT3, TT4, and TT5. In autocross SCCA A/Street (well, there used to be A/Street CRs), B/Street, STR, and DSM (with 315/30 Hoosier A7 tires). Plus large numbers of owners running track days. You could PM them for their specific recommendations.