I’m not a graphic artist so I can’t speak to the first two questions at all, but I can offer input on 3 and 4.
3: Yes, you can have sublevels load in and out asynchronously with sublevels: Collaborate with Sublevels | Unreal Engine Documentation. Sublelevls load in and out quite quickly, so you don’t need to worry about unloading things too early. They will load back in a matter of seconds. But you have full control over when to load or unload them. If you prefer to let the engine decide, you can place volumes that will load and unload levels depending where your camera is.
4: Depends on what you’re looking for exactly. Do you want to make an entire blueprint invisible? Just set “Actor Hidden In Game” to true at runtime. If you want to turn it off completely (i.e. not running any logic) then you’ll need to turn off Tick on the actor and all of its components.
iTween : Free, smooth, procedural object animation
easyCSV : Read data from any CSV and put them in an easy-to-access string map!
Runtime DataTable : Import and export game data to and from CSV or Google Sheets while your game is running!