Starvation detected in WASAPI output buffer - This means that the mixer was too slow to output sound briefly. If you are running the UE4 editor it isn’t a big deal since it might well occur if the editor is loading something or exporting, which might cause a CPU spike.
If you see it in a real game, then it means that the mixer graph is too heavy and the sound may drop out.
The missing DSP plugin message usually means that the plugin hasn’t been loaded, but again in the editor it is something that can be ignored. That is because in the editor itself, we don’t load plugins (we do for PIE though). That was to ensure maximum stability in the editor regardless of what plugins are loaded, but it does mean that those warnings appear when starting up the editor.
If you see it in PIE or in game it means that the plugin hasn’t been loaded and then indeed sounds may not play. If you are using the Oculus plugin you can enable the oculus module. For deployment of plugins, see these pages:
http://www.fmod.org/documentation/#content/generated/engine_ue4/plugins.html
http://www.fmod.org/documentation/#content/generated/engine_ue4/deployment.html