Deleted my previous posts prematurely - I managed to fix the issue with the plugin not working as an Engine plugin (just compiled as a project plugin then moved the binaries over), however, that did not fix the problem with the plugin working only in editor and not in the packaged game.
Here’s the error:
LogStreaming: Error: Couldn’t find file for package /Script/UnrealFastNoisePlugin requested by async loading code. NameToLoad: /Script/UnrealFastNoisePlugin
And as previously mentioned, if I change the setting from Developer to Runtime, I get an error on compile:
LINK : fatal error LNK1181: cannot open input file ‘C:\Unreal Engine\UE_4.18\Engine\Plugins\UnrealFastNoisePlugin\Binaries\Win64\UE4-UnrealFastNoisePlugin.lib’