Technically, there is no single style of wrestling in Joshi or Japanese female pro wrestling.

Generally, the reason Americans and others abroad often differentiate Joshi wrestling as a style, it's usually because Japanese women's wrestling is generally stiffer (strikes hit harder), involves more impressive techniques, and just overall of a higher quality than pro wrestling in America.

As far as a specific style, however, Joshi wrestling organizations - and individual wrestlers or even each match within the same promotion - can vary from "hardcore" (comparable to a Mick Foley or Sabu match in the US) and comedy matches to technical submission-based or hard-hitting strike-driven matches. So there is no single style that differentiates Joshi wrestling any more than "American style" could accurately summarize 1990s ECW together with present day WWE.