I have two APNs in my settings and both are active. My network mode is set to LTE/CDMA.
If you're not roaming outside the US I can't see any need to have global enabled, however I also don't see why that would cause any issues.
Oh and by active I mean if you tap one of the APNs and scroll to the bottom you will and line that says 'active'.
From the main APN neither of mine have the radio button enabled. I haven't touched these settings so these are the defaults.