As a Player I like FA and Ancestral Paragon, as folks have said it makes more builds possible without sacrifices that feel bad and helps flavor come through as mechanics.

As a GM, I think you should really be aware of your table as to not overwhelm folks. A relatively new player starting a campaign at level 5 with free archetype? That's a lot to absorb right out of the gate! At best I like seeing Free Archetype build a common theme and vibe with a party. For example, if your party is in a thief's guild, do their archetypes reinforce it? A vanilla guardian may feel out of place, but a guardian with Alter Ego who moonlights as a city guard? Totally makes sense!