As far as weights are concerned, would a 4 or 5 be ok for panfish and bass? Mostly ponds. Also what kind of main line is the best? I'm going to be using top waters and sinking flies mostly. I need to get a reel re-spooled. Thanks for the help!

For ponds, either is fine. The big limiter here is the size of fly that can be cast. And casting. A five weight will be slightly easier to cast than a four. Just a bit more weight to work with.
If you get a chance to, test cast both, see what suits your needs best.

5 would be better on windier days. I prefer orvis hydros bankshot it has a short taper so it can turn over big flies and also will minimize the amount of false casts. some people use rio outbound short i just could not get over how stiff the line is and switched to the orvis line.

I agree , either size will work but 5 wt in wind is better . I use a Sage VXP 9-ft , 5wt and an Orvis Access with their Trout line . Got 5wt line but could probably work better with 6wt especially if I have longer cast .

I'd go with the 5 weight. I have heard the 9 foot 5 weight is the best-selling rod in the country, so that should tell you something. I have rods in weights 4-6 and feel the 5 is the best all around choice.