Matchlocks were the cheaper, more common longarm in armies of the period, but "sparking" arms - snaphaunces, wheellocks, flintlocks, etc. - had been around since the late 1500s. Very few Highlanders (and I assume that's who we're talking about, not Scots in general) could afford firearms, only the upper-crust "clan gentlemen" being able to do so. Their longarms were primarily hunting pieces, used in war only secondarily, and were by and large NOT matchlocks, which were mostly a military weapon. Snaphaunces and early flintlock forms were the preferred long guns of the clansmen - again, the ones who could afford them! - a small percentage.
The fowling piece I have in the photo is a Dutch gun, with a lock that dates to pre-1630. Scotland imported lots of arms from the Low Countries through her eastern seaports.
Bear in mind that highland "clan regiments" were a different animal than the typical army infantry regiment of the civil wars. The latter, which might include some highland soldiers, featured issued weapons: pikes and (mostly) matchlocks. The clan regiment consisted of a front rank of fully-armed clan gentlemen with the aforementioned personally-owned firelocks, broadswords, and targes; the remaining bulk of the men armed with polearms and a smattering of captured firearms.