Is there any difference between the two? They seem the same to me, c.f.:
Fußball spielten die Kinder vor der Schule im Park.
Football played the kids before school in the park.
(sentence from wikipedia).
OVS word order means that the object comes before the verb and the verb comes before the subject. It's not very common, for reasons relating to branching direction. But in an OVS language it doesn't matter what else is on the left side of the sentence: you can put prepositional phrases there, or adverbs, or anything else you feel like. The object just has to be somewhere before the verb.
V2 word order means that the verb comes second, without specifying what comes first. In German (and Old English and some other Germanic languages), anything can go first, whether that's a prepositional phrase, or the subject, or the object. What's important is just that it's one and only one phrase.
To quote another example from the same Wikipedia article:
Die Kinder spielten vor der Schule im Park Fußball.
[SUBJECT] [VERB] [PREP PHRASE] [PREP PHRASE] [OBJECT]
This wouldn't be grammatical in a purely OVS language, since the subject comes before the verb, and the object after.
On the other hand, if we take a sentence in imaginary "OVS German":
Vor der Schule Fußball spielten die Kinder im Park.
[PREP PHRASE] [OBJECT] [VERB] [SUBJECT] [PREP PHRASE]
This would be grammatical in "OVS German", but not in actual V2 German, because the verb isn't second: it's third. Two things come before it, and that's not allowed.