Version: Spigot 1.8.8 Tests: During Day: Above void: 1-2 Seconds Above air, but blocks 5 down: None Above ground: None During Night: No lag Plugins: WorldEdit, FrameProtect, CombatLog, Votifier, Sinister, WorldGuard, SignEdit, ColoredChat, PermissionsEx, ViaVersion, Firework, Vault, GAListener, TimeLock, Essentials, RegionTeleport, CommandSigns, ProtocolLib, HideAndCustomPlugins, NoCheatPlus, ChestCommands, EssentialsProtect, EssentialsGeoIP, Mobcash, EssentialsChat
I know that getting rid or placing block at the void level indeed causes lag issues for the client. When you break the block, you're able to look into the void. When you place the block again, the view to the void gets blocked off. This is simply Minecraft's performance issue. I have a monster PC and even I have that issue, it's normal. Don't build at void level