Ok, so minus the bulk which I realize now it could be considered both would it be considered the same? Yes, you would consider me a noob on these sorts of things.
CCI makes a variety of 22lr ammunition, and for the most part, it would be characterized as 'bulk' ammo.
Your 15-22 will shoot almost any 22 long rifle (lr) ammunition. You can spend a lot on match ammo which will provide better 'groups', but since the 15-22 does not have what it considered a 'match barrel', most will purchase whatever they can that is reasonable in price.
Cabellas has CCI Blazer for $0.05 a round, which in our current circumstances, is good, if not great.
In short, I wouldn't worry about whether you are shooting 22lr that might be considered 'bulk' or 'not'. Your rifle won't know the difference (in most cases). The person next to you at the range won't care. Only your wallet will care.
The general recommendation is to try a bunch of different ammo. Buy a brick of CCI Blazer. Buy some Remington Thunderbolts. Buy some Winchester. Shoot them, and see which one your rifle likes best. It may like them all, it may prefer CCI over Thunderbolts (mine has failure to feeds occasionally with thunderbolts, for instance - so I save those for my bolt action, where it always goes 'bang').
The only caveat is stay away from ammo that says 'not for use in semi-autos'. These are generally 22lr rounds that are subsonic or do not provide enough recoil to reset the hammer/trigger, or don't bring the bolt back far enough to capture and load the next round.
Bottom line, get as much as you can for as little as you can.
I hope this helps, and welcome to the addiction!