Mate..
Only 12s are unrestricted these days..
14s have a hoist height of 7626mm with rule 13.e.1 stating "The foremost end of the spinnaker boom, including end fitting(s), shall not extend more than 2743mm beyond the foremost vertical extension or transverse extension of the bow.").
With 16s the rule is 7.12 which states the maximum length of the assymetric spar may not exceed 2700 mm measured from the stem..
There are two 18 foot skiffs these days the "Bethwaite" camp and the "Murray" camp..
The league 18s have rule 11 which states in part "Any pole has a maximum length of 3.8m (12ft 5in) from the stem."

In regard to rigs many 14s do in fact have rigs that are adjustable uphill and down.. Cranking on the stays tightend the uppers and pulls the rig tip back..Some even have an adjustable setup that allows the rig to lay back as required.. Ie adjustable forestay and side stays..
As do many Javelins and Cherubs.. The old 18teens did as well but with Bethwaites strict one design rules these were basically banned.. The 16teens walked the same path as Bethwaites's 18teens..
I dont believe the any 12s have an adjustable rig.. But then I wouldnt like to be trying to adjust much with that much rag up..
But no matter which skiff it is one will find the rig is designed to be far more gust responsive than any cat rig..

Yes skiffs are slower than a cat when one looks at the ratings.. Apart from the 18teens vs a 18 foot cat.. But Im sure a 12 footer crew will also tell you that its far more lively than any cat..
I will stick my neck out here and suggest..
Any of the top 12 footer crews could easily jump on a Tornado/F18/F18HT/F16/M20/F20/F20HT and take her around a course without swimming.. In fact it would be a cake walk.. I would further suggest there isnt one top cat crews who could do the reverse (unless they have a reasonable amount of skiff experience)..

just my thoughts..