I haven't used Galaxy but I'm almost certain the answer is yes since Galaxy doesn't have DRM like other store clients and you see Galaxy related dlls in the standalone installers as well so I'm guessing the integration is the same either way and doesn't cause trouble without Galaxy present. As of semi-recently you can buy games on Epic via Galaxy but if they are DRMed you still need the Epic launcher to play them since GOG won't add DRM to Galaxy.