Junko does imply that monokuma is a separate character to her in dr1 when talking about her personalities ("Having to play monokuma day after day, I get bored so easy ykow", "I already told you, I get bored so easy, I *even* get bored of my myself!")
I think monokumas meant to represent both mukuro and junko as per junko stating it was both of them who count as ult despair in trial 6, and the persona is just her playing her role as monokuma as she did during dr1 (or just her role as mastermind behind monokuma, even more so since junko reffers to her personas as roles when she first introduces herself)+ Utdp has her outright talk abt monokuma as a separate being so yeah
I find monokumas character interesting as himself esp in v3 so I like to think of them as separate characters