Terminal Meta functions just need to be unlocked and upgraded at least one level each (where possible). Maxing out is not neccessary. However maxing out at least the "Meta Chip Multiplier" is highly recommended, because you will need many of them for unlock all armarments.
Because for the armarments, you need to unlock every single one for all sentinels each. Leveling up the armaments is not neccessary.
Meta-Chips are earned in both Adventure and Combat Mode, the majority in combat however.