These are centralized application services rather than school-specific portals. AMCAS handles the primary application for almost all MD schools nationwide. AACOMAS handles DO schools. TMDSAS handles the public medical schools within Texas specifically, MD and DO alike.
You complete one primary application per service, and it gets distributed to every school you select within that system. Each service has its own essay prompts, formatting rules, and deadlines, so budget separate time for each service you're using rather than assuming they overlap.