1. I totally disagree with you.

2. I totally don't agree with you.
(Are both the same? Or are both different in meaning?)

Both mean the same.

Both sentences convey a similar meaning, but there is a subtle difference in the emphasis or intensity of disagreement.

1. "I totally disagree with you." - This sentence indicates a strong or complete disagreement. It suggests that you have a fundamentally different perspective or opinion from the person you are addressing.

2. "I totally don't agree with you." - This sentence also expresses disagreement, but it may not necessarily imply a complete opposition to the other person's viewpoint. It could mean that you partially disagree or have reservations about their opinion.

In summary, while both sentences express disagreement, the first one (I totally disagree with you) suggests a more intense or complete disagreement, while the second one (I totally don't agree with you) can encompass various levels of disagreement.