Yeah. There is no simple answer to that. It all depends, as we so often say here. See MattZ's answer. You don't tell us anything about intensity, volume, frequency, etc., etc. It might be fine for one guy and not another.
"Is this too much variation of movement?" No, probably not. There's really not much variation. BB bench on one upper day, DB bench on the other. BB press once, DB press once. No big deal.
"Is it acceptable...?" Acceptable? In what sense? It's acceptable, but not because its variations of the same movement. It's acceptable because you have already said you're getting good results. I don't really see that there's an issue here.
And I don't think it's that bad of a template, overall, either. I assume you plan for adequate rest within the training week.
But isn't there a general guideline for whether to perform different variations of a movement on different days within a week, or repeat the same movement varation (say, barbell back squat, instead of alternating with front squat)? Lets say assuming the volume and intensity would be the same in either case.
No, I don't think there's any such guideline.
Variety is good, but you can vary things within a template, within a day or over time. It's all up to you! Some things make more sense than others, but it comes down to what works for you.