From YoYoWiki:(Styles Of Play | YoYo Wiki | Fandom)
Freehand Offstring
Also known as 9A (5A plus 4A),
A counterweight is attached to the string, but the yo-yo is left unattached. This allows for a fusion of 5A concepts with 4A concepts into one trick, into one unique style. Notable players of this style include Ryan Lai.
7A is 2a with counterweights.
8A by your description AKA Soloham would be effectively 4A with 2 yoyos. You’re basically using either one long string(half would for each yoyo), but is usually each yoyo has its own string for the purposes of throwing/binding, but one string is used primarily for tricks.
The variety is somewhat limited, but the trick possibility is infinite due to the various existing and not yet explored styles yet.