Sorry to be a bit late to this.
I'd say that a type set's scope is defined by an individual collector and their interests. For example, when it comes to silver, I'm not particularly interested in silver varieties (which are anyway "micro" varieties), and would settle for one of each denomination.
As far as bronze is concerned, any variety collecting would start - and possibly end - with the LT as those were very definitely a first 'type', replaced by the high tide. For halfpennies and farthings, that's pretty much it. For pennies you could go down a very long road, starting with an 'open 3', the 1905s, all those 1908-9 rarities, etc.
There's nothing to stop you having a basic type set of each denomination, then constructing a full set of pennies if that takes your interest.