I can give you some hints, just keep in mind I'm not a specialists of any kind.
Well, Hajduks were core of infantry both in Hungary and Poland. As for their tactics, there were changing with time but certain things remain "stable". Hajduk were armed with arquebuses (later with muskets) and bardiche used during fire as musket rest.
It seems that usually after firing a volley or two they were taking their bardiches and charging at the enemy. They did so for example in Battle of Lubieszów 1577. In this battle hajduks manage to break more numerous german pike and shot infantry. At first they shoot a volley from their guns and then used bardiches to cut the tips of german pikes. Without protection of pikes hajduks had an easy job with cutting down the enemy infantry. As curiosity I can add that hajduks used exactly the same tactic (with some minor modifications) in Battle of Vienna in 1683. So it seems it was effective. But I should add that ther were also unit s of hajduks that didn't used bardiches but only sabres.
In terms of firing and formations: Hajduk units were usually forming in 10 lines with 10 or 15 soldiers in each line. This give us 100 or 150 in each unit. Such units were part of bigger formation known as banner. Each line starting from the first after shooting the volley was crouching to allow the line behind them to shoot. As you see it's a different tactic from countermarch.
About Hungarian rouster:About Hungarian roster: Well I think in order to remain balance you could remove Ungarische Arquebusier and replace them with Hajduks armed with arquebuses and bardiches or sabres. As for Uskoks. In your place I would leave them as lower tier unit, with less organization and morale with one handed axes or with sabres(and fire arms of course). Since Uskoks were refugees, that had a role similar to polish cossacks and since they were more like pirates and skirmishers you could make mounted version of Uskoks to fill the gap after dismounting hajduks, you know for balancing purposes.
Unfortunately it's hard to find good representations of hajduks from XVI century
This one is from the beginning of XVII century.
This one show Transylvanian army, unfortunately also form XVII century. You can see hajduks below hussars.
And another hajduks: