Polish accusative case
Do polish people pronounce the Ą and Ę at the end the accusative form of nouns? or do they just pronounce them like a?
ą - yes, definitely.
ę - if it's the final sound of the word, then most people don't.
The question about how ą and ę are pronounced at the end of a word has actually nothing to do with the accusative case, as ą also commonly appears in the instrumental case and both ą and ę are very common conjugation endings for verbs.
About the pronounciaton of word-final ę:
The historic and now hypercorrect word-final pronounciation is [ɛ̃w̃]. Most speakers nowadays pronounce it withouth nasality as a plain [ɛ]. It is also considered correct to retain a very subtle nasality, which I do, too.
There are some regional/dialectal deviations to this, but unfortunately I'm not qualified to elaborate on this topic. Maybe someone else has some insight.
About the pronounciation of word-final ą:
The standard Polish pronounciation is [ɔw̃]. However, many speakers denasalize it, pronouncing it as [ɔm], which I heard quite often in western parts of the country, or as [ɔu], which seems to be more common in eastern parts.