Hey,
Quick answer as Paris is my city. As long as you don't go in the suburbs (and I don't see why you would go there) it's fine, just avoid the north of Paris and the Champs-Elysées between 0:00 and 5:00am. Some PSG mob usually hang on game day around Bastille, however they usually don't attack scarfers and normal fans so it's safe to go and there's many good bars. Good places to have drinks can also be found on Chatelet and Odéon/St-Michel, that's usually where away fans go. You won't have problem to move in the city by subway, it's very well served and subway stations can be found almost everywhere; just remember it close around 1am on week days. Single ride tickets cost 1,80€, but there are many other tickets such as daily ticket which cost around 7-8€. All this can be bought in the subway station directly on automatic machine, you can set english language. Parc des Princes subway stations are on lines number 9 (Porte de St-Cloud or Exelmans) or 10 (Porte d'Auteuil); atmosphere in the stadium will be shit as there is only clowns and picnic fans going now.
Have a good trip
