Thanks, this helps. If I were to use my Sangoma S705 phones (rebadged HTEK UC926E), is there anything else I would lose? For example, what about paging, DND, call forward, etc? I'm very new to both FreePBX and 3CX; I'm sure this is pretty basic stuff.
Mostly yes. I recommend reading through the guides or just spinning up a trial instance. All of those are available in various fashions either via star code, BLF, or via the apps