soft pies

That depends how much time you are willing to spend on last minute assembly. The ideal way of making these pies, would be to bake the crust and make the filling ahead, but kept separately. The fillings should hold fine in the fridge for three days. You can make the pie dough well in advance and freeze it. If you do want to bake it ahead, it should keep, well wrapped for several days.

If it is possible to assemble them within 4 hours of serving them, that is great. Otherwise you can brush the baked crust with melted white chocolate or cocoa butter, this will create somewhat of a barrier from the moisture in the filling, but still try not to assemble more than one day in advance.
For the whipped cream, you can add a little gelatin to help it keep its shape or use a higher-fat cream, like manufacturing cream. If using meringue, try an Italian meringue for more stability. It should keep well, on the pie for 24 hours.

 

Keep in mind, the meringue I am talking about is an Italian meringue. That is where you add a hot sugar syrup to the whipping egg whites. This "cooks" the whites and gives them a slight marshmallow-y texture. The meringue will hold up better and can be browned on top with a torch.
For the filling, you should have one that is firm enough to hold its shape once the pie is cut.

 

Stabilized whipped cream....I put my stand mixer bowl and whisk in freezer for about an hour,,,whip 6 cups heavy cream to soft peaks then add 2 1/2 cups powdered sugar (I sift the sugar to avoid lumps in finished product) and beat on high to stiff peak stage. I like to add a bit of flavoring in with the sugar...vanilla from the bean if I am feeling particularly flush...

 

I don't know how long it will hold...never had any left. I would be more concerned with the pie filling. Custards will start losing quality after about a day in fridge.