Yes, this should be fine assuming you set it up correctly. For multiplayer, i wouldnt go much bigger, asusming your using a solid single map. If you split it up, watch your map size. I remember there being a replication issue with things that fall outside of XY 1,000,000 to -1,000,000. This may have been resolved, but, i do remember having issues on the client side (players falling into the map as soon as they hit like 1,250,000 XY, things not displaying properly, culling distance being slightly “off” for distance, etc). I havent REALLY messed with it since 4.7, so, like i said, you would have to test this yourself.
Thats up to how well you design your server and the network solution you use. Will the default network solution (posted all over the place with youtube videos) work for more then like 50 people? Probably not. It may tho, depending on how well your server can deal with the code and how big/small your data is. It’s really a factor of, well, everything.
You can use 100 LODs if you wanted. up to you, no reason to stop at just 3. If you need more, make more! I am using 10 LODS and distance factors in the grass alone, so, feel free to use what works best for you and your project.