Something to consider for 223/5.56 powders, especially in an AR, is bullet weight and barrel length. Light bullets in a gas carbine with powders like 748/BLC2 are going to be slow and dirty.
Most data is for 24" bolts, or 20" AR's, dont be mislead by slight higher velocities with those barrel lengths and those powders, if you have a carbine.
This is where QL is fun to play with, instead of barrel length, I'll plug in the length to the gas port and look at powder burn % and velocity and compare it to burn % and velocity of barrel length.
Is H335 the fastest or cleanest, no, but it is in the top 5 every time.
And I know H335 is one of the most produced and widely available powders. You can almost always find it.