You can use conditional fields in the success or error messages as well.
Example form:
[radio r use_label_element "show success message 1" "show success message 2"]
[group s1][/group]
[group s2][/group]
[submit "Submit"]
Conditions:
show [s1] if [r] equals "show success message 1"
show [s2] if [r] equals "show success message 2"
Now, under the Messages tab, you can use group tags to determine which success message should show depending on the group that was visible during form submission.
Result: