Michaels is the de facto standard two-suited overcall, and we use it
against every natural opening, even a minor suit that may be as short as one
card. Showing both majors keeps the auction low and secures our heart fit.
Note that natural openings are protected from brown stickers. Only over an
artificial opening can we cue with 5-5 including opponents’ nominal suit.
Balancing overcalls tend to be intermediate. Jump overcalls are sound because
there is no one to preempt. On the other hand, constructive overcalls are light
because partner may have passed a weak notrump.
An unpassed 2NT is no longer unusual because we’ve got more steps on the notrump
ladder.