WP is great because it’s automatic, and tune-able. But it’s not subtle. It really depends on your exact requirements. With things like streaming and level instances, you have more control, but you have to do more.
Like you say, great for loading and unloading things. Lights you don’t need to worry about. Even though they do get unloaded, you can always just set the maximum visibility distance, and done.
LODs again, useful. HLOD is for grouping lots of assets, so it’s a sort of super-LOD. So at great distance the player see the HLOD, then separate objects, but low quality LOD, then higher quality etc.
The thing is with HLOD is, if you’ve destroyed a building, for instance, you also need an HLOD of the destroyed area, for when you come back. Again, it really depends on what exactly you’re doing. From what you’ve described, mostly indoors, I wouldn’t bother. LODs are also automatic.
The best thing is to have a hack at several of these methods. Just make a bit level and stick a load of rubbish in it. Does it work the way you want? Tune it a bit, try another method. Etc. Before committing to early to a particular path.