A question about Archiving.

I'm a Pro member, DM. I'm creating a "Living Forgotten Realms" D&D 3.5 campaign for my players. I've already imported tons of maps, tokens, characters, handouts, ect. Being a Pro membership, do I need to worry about the size or uploaded content into my game? Will the dynamic lighting settings or, number of uploaded maps and encounters begin to bog my game? Should I be Archiving unused encounter maps or unused folders, characters, ect?

Archiving content does nothing for the campaigns performance, only hides them from view. Some pro users keep "storage campaigns" where they keep some unused maps/characters/etc saved and use the transmogrifier to move stuff back and forth now and then. Your storage limit can see from you account page, and shows how much you have left. How full this account-wide limit is does not impact performance of games at all.

The way Roll20 works is everything that is in a game is loaded into memory when a player joins the game, including anything that is 'archived' within the game .  So the in-game 'archive' (for both map pages and items in your journal) is simply a way of organizing items to remove them from being visually distracting, but they are still going to impact performance. Because you have a Pro subscription, the better approach is to create a 'prep' game where you can set up Dynamic Lighting lines, maps, tokens, etc., and Transmogrify those pages and things into your active game when needed.  Then after you've finished with a page in your active game, Transmogrify it into a different 'Archive' game and delete it from your active game, so that you can move it back to your active game in the future if needed. That will keep your active game as lean as possible for the best performance.

Obligatory  Tips and Tricks  link:  Library Campaign