I always mumbled as kid & now slur. mainly self esteem issues. if it was tongue issue caused by als, ms, stroke would i be able to change voice tone?

You would still be : able to change vocal pitch, tone & loudness if solely a tongue issue. If you're concerned about low oral motor muscle tone &/or weakness, a neurological exam will reveal these. If you had mild dyspraxia, or Developmental Coordination Disorder, as well as Developmental Articulation Disorder as a child, it can persist into adulthood. An occupational & a speech/language therapist can still help you.

Probably yes: In those conditions, people can modulate their voice and change the tone. Sometimes those illnesses do not affect the voice at all. Sometimes those illnesses result in a person being unable to speak.