I was quite keen on what I call the stuff with splodgy greenish bits - it's similar to methods used at Mdina, but cased more heavily and possibly at a different temperature, so what would have been yellow goes a bit green because of reacting. Sometimes, it is found with bits of dilute cobalt blue though it too.
I do believe the "greenish splodgy" is early Mtarfa. (It does come in "greenish swirly" too.) It predates the weird coiled neck bottles and strange gate-style type sculptures, and is definitely before Mtarfa got a bit more sophisticated and started coming up with their own original designs.