DayZ like terrain

What is the max size for multiplayer?
I ask because im working on some things and im about to post some questions … not to hijack …

Whats the best method for setting up an open world, tiled, landscape at high res?
Can i do an 8k res @ 64kx64k ?
If im using tiled, what if someone is on a mountain and looks out, will the distant tiles be “missing” due to the player not being X unreal units away from that tile, so, its not rendered in?
Can i setup a single heightmap @ low res (say 2k) and use that as a “blanket” (call it Map1) on my tiled map set (map2) to 8k res and set the res in-game for “map1” to super low? This should allow the landscape to always be seen, but, just super low res. Rendering in the high-res as people get closer and closer to the tile … right?
Would that just add more weight to the map itself, effectively lowering FPS due to having to load in 2 maps (or 1 fulle map +X amount of tiles @ high res)…

etc etc etc … lol