BmMaj9 is B, D, F#, A# and C#. It keeps every note of and adds the .
BmMaj9 and both contain the 9th. The difference is the 7th: BmMaj9 uses , while uses the flat 7th.
Choose between them by the seventh under a held 9th. The minor 3rd remains in both chords.
Also written BmM9, Bm(maj9) or B-Δ9.

Drop the third voice from the top an octave instead. The wider gap skips a string, so the muted string is part of the shape.
That result, 3–R–5–7, is the shape usually meant by drop 3. Named by its bass note, as the inversions are here, it is the 1st inversion.
More familiar jazz shapes are drop 3 than drop 2.
How you get to it. The turn that lands on BmMaj9 is to : the ii and the V of B minor, which is where a minor tonic is usually arrived at rather than simply begun on.
Hear it land:→→
Contains BmMaj9 and adds eleventh and flat thirteenth.
Contains BmMaj9 and adds eleventh and thirteenth.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.