Mr. Clayton was pretty committed to Obligatos for a few years and I know he was testing Evah Pirazzis, but the last time someone asked about them when I was around he was non-committal about what he thought yet. I don't know if he stuck with them or not. I thought he sounded better with Obligatos, but I never quite understood how he was able to keep Obligatos together under his heavy hands.
I don't believe that he's used Spirocores in the last 6 years or so, that I've had some limited access to him. I think he endorsed/was endorsed by Thomastik Superflexibles before Obligatos.
His main bass is Ray Brown's old bass with violin corners and it's a fine instrument and his tone is mostly influenced by his awesome technique, which he also inherited from Ray Brown. He walked into a rehearsal I was in once, took my bass in the middle of the tune, turned off my amp and told me to go across the room and listen. He sounded like him, not like me and said I didn't need the amp. So, anyway, his strings or even his bass will not make you sound like him. Learning technique through arco is a good thing to do, but if you're working pizzicatto and are struggling, you need a lesson in it as well.
It's tough to get more articulation via strings than with Spirocore Weichs. If anything, you might try Spirocore Mittels, but they're going to be a bit more work under the bow. In my experience with EP Regulars, you will certainly get less articulation with them, than with Spirocores. They have a thing and it's cool, but it's not clarity over Spirocores.