It does depend somewhat upon the rib design, but since I don't particularly
want any road spray from wet roads blasted in & under my Spyder, ie. immediately into the path of the rear tire...

. I generally mount tires with tread designs that matter so that the majority of any road spray is going to be pushed out & away from the rear tire. :yes:
As for your choice between tires &/or swaybar, if you are still running the OE Spec Kendas, then arguably the greatest improvement for cornering will come from tossing the OE Spec Kendas & fitting a pair of good quality tires up front, and running them at an appropriate pressure for the (much lighter) loads they'll be carrying.

hyea:
Yes, a swaybar upgrade will make a noticeable improvement to your cornering too, and if you are already noticing the limitations of the OE spec swaybar, then you'll also want to do that in due course; but without fitting better tires, any handling & cornering improvement the bar upgrade might bring will
still be limited by the relatively pedestrian performance of the OE spec Kendas. :gaah: Of course, if you never try to push up to &/or beyond the Kendas' (fairly restrictive) limits, you'll likely never really notice any cornering improvement per se, but with either upgrade you should still notice some better stability, ride, & handling, etc, and most car tires run at an appropriate pressure will also give you better tread life, puncture resistance, suspension compliance, et all! :cheers: