A few in more detail...
The M91 is used with the M327 high explosive plastic tracer (HEP-T) (high explosive squash head [HESH] in UK parlance) projectile that is projected by various 105 mm howitzers (M2A1[M101A1], M2A2, M4, M4A1, M49, T252).
M91 and M91A1 M66 HEAT-T projectile that is projected by the M1 series of 75 mm pack howitzers.
M91A1 used with M310A1 HEAT-T and M349 HEP-T projectiles that are projected by the M20 & T21E12 75 mm series of recoilless rifles.
M91A1 is used in M326 HEP-T projectile that is projected by the M27/M27A1 105 mm recoilless rifles.
M91A1 used in the T142 and T142E3 90 mm HEP-T for M36, M41, M54 (T125), M1 series and M2 series 90 mm guns.
M91A2 is used in M346, M346B1, and M346A1 HEP-T projectiles that are projected by the M40 106 mm (really 105 mm) series of recoilless rifles.
M91 has an integral pressed-in tracer, whilst the M91A1 and the M91A2 use the M5A2B1 screw-in tracer.
The M91 series are similar to the M62A1, differing in than the M91 series have a tracer.
The dummy fuze for the M91 series is the M86.