The SCCY design is pure double action but hammer instead of striker. They are ultra-safe as it is nearly impossible to have an unintentional discharge with a SCCY, even more so with the CPX-1 (9mm) which has a separate safety lever that disconnects the trigger from the hammer. But the long heavy trigger pull (about like a revolver's) does take some getting used to. Even though inexpensive, they are very well-made and reliable pistols. They won't win any shooting matches, but that's not what they were designed to do.
They're good enough mechanical clones (and better, cosmetically)
of the Kel-Tec P-11, that Kel-Tec discontinued making it.
Neither the PF-9 or the P-11 is a "double action striker" gun.
Both are DAO, trigger-cocked hammer actions. The PF-9
uses a 'semi-cocked to full cock' action, with slide action
required between releases, while the P-11 mimics the DA
action of a revolver (infinite restrike ability).
The only "double action striker" pistol I've encountered was
a small 9mm Taurus. Met a gal at a range who had one, and
was learning how to shoot. I handled it briefly and was
surprised to realize Taurus had incorporated something in the
design to draw striker back far enough (seemingly) to build
up enough spring compression to pop primers...or so it
seemed, from casual handling. I didn't take it apart to
investigate it in depth, and don't remember what model it
was.