Camillan and Polybian Armies

[Arjos]

Did the Camillan armies basically use Samnite Hastati, Etruscan Hoplites, Campanian Cavalry, Lucanian Skirmishers etc as their allied forces?

More or less, not solely those you mentioned but whatever members of the Latin League and later the various communities/polities allied to Roma were called to supply men...
Obviously they employed them according to their cultural experties in warfare...

For the Polybian Armies, did they use Socii Hastati, Socii Principes etc?

In Italy, yes, for the various communities were ever romanized, even though they did keep their distinctive decorations. But Polybian armies found themselves engaged far away from the Italian Peninsula and usually the allied contingents, were drawn from whatever local population they were in contact. Being them Iberians, Greeks or Numidians for example. Of course at the very beginning of the campaign, soon as the Consvl received his Provincia (in the sense of "territorial" mandate), he would depart with a moderate core of Italian troops (something like two roman legions and two from the socii) and wherever he was headed, would see him joining up either with local allies already on the field or the Consvl would gather new forces there...

My final question is, when exactly did the Romans make the change from Camillan to Polybian armies?

It is very much debated and I don't think there will ever be a clear answer. It most likely was a gradual process stretching from the wars with Keltic tribes in the Po Valley, to the Second Punic War. That generation of people fought pretty much non-stop for all their mature life. The pilum and gladius were adopted, also thanks to loot and something of a "war economy" definitely more citizens could afford more sophisticated armour, like chainmail. Consider how Polybios records about the roman eagerness to attack "barbarian" tribes, due to their jewelry and later the private contributions to the Senatvs for the war against Hannibal in Italy.
It was certainly a time in which Latin soldiers were not engaged in seasonal campaigns in the Italian Peninsula, but wintered oversea for few years and they were generally "professionalized"...
Iirc in the Macedonian Wars there still were veterans from Cannae fighting, not mentioning Africanvs' men way back from the campaign in Hispania...

In a nutshell: the more successful campaigns a citizen took part in, the more resources he acquired (both direct and indirect, new trading opportunities, new grants of land that sorta thing). While foreign arms were appreciated for their properties and studied. Manufacturers through trial and error or even foreign specialists, would copy and improve the new equipment etc...

There are some arbitrary dates like Cannae, but at least in my view it is a bit ludicrous to imagine that one day the Romani said to themselves: "You know what, these weapons are rubbish! Let's make completely new arms by tomorrow!"...