Can I prepare store bought puff pastry with filling and then fridge it for a few hours before baking?

Yes, you can (with certain recipes). To simplify your day, you can prepare the recipe ahead of time, then bake as directed prior to serving.

Personally, I wouldn't leave it too long in the fridge. The filling might make the pastry not rise as high. You could always make individual cups, bake ahead of time and then fill with pudding and the filling. You can make an easy cream cheese pudding:

Mix together 2 cups milk and small box of pudding mix with hand mixer. Add softened/room temperature 8 ounces cream cheese to the mixture and continue to blend well with hand mixer. Mix until smooth, transfer to small container or individual containers, and refrigerate for 15 minutes.

Yes. Most of the time I use puff pasty I put everything together, refrigerate it for later, then bake.

Sure.