If you buy the module here on Roll20, it comes with everything in the physical book converted to handouts and/or compendium entries (this varies by module). Dynamic lighting is already set up, enemies are already placed. The game the module creates is pretty complete and ready-to-run wit the D&D 5e by Roll20 character sheet in the game. If you use another sheet, things might not work right or may need a lot of manual work to clean up.
You can get an idea of what they are like by grabbing one (or all) of these free modules:
The Sunless Citadel (free until May 14th): https://marketplace.roll20.net/browse/gameaddon/157/the-sunless-citadel-tales-from-the-yawning-portal
The Forge of Fury (free until May 21st): https://marketplace.roll20.net/browse/gameaddon/154/the-forge-of-fury-tales-from-the-yawning-portal
Explorer's Guide to Wildemount Adventure Preview (always free): https://marketplace.roll20.net/browse/module/5353/adventure-preview-explorers-guide-to-wildemount
The first two are Addons, which can be added to an existing game (see https://wiki.roll20.net/Game_Management#Game_Addons). I would still recommend adding to a new game instead of your existing game as there is no easy way to remove everything if you don't want it in the game.
Explorer's Guide to Wildemount Adventure Preview is a module. It's a little larger so it can't be added to an existing game. Instead, you start a new game with the module as a basis. See more here: https://roll20.zendesk.com/hc/en-us/articles/360042178613-Accessing-Managing-Marketplace-Content#AccessingMarketplaceContent-Modules