Is the best team all similar personalities or diverse?

Diverse, but intentionally. A team needs strategic thinkers (INTJ), execution-focused people (ESTJ), relationship-builders (ENFJ), and detail-checkers (ISTJ). All one type creates blind spots. Diverse teams outperform homogeneous ones on complex problems, provided they communicate well.

How many of each personality type should be on a team?

For a 5-person team: one strategic thinker, two executors, one relationship-builder, one detail-checker. For a 10-person team: two of each. Ratios matter less than intentional balance. Avoid all quick-decision-makers (recklessness) or all consensus-seekers (no decisions).

What if my team already exists with mismatched personalities?

Work with what you have. Role-assign based on strength: the detailed person handles quality, the relational person handles clients, the strategic person handles planning. Make personality diversity explicit: "We think differently—here's how that helps us." Leverage differences instead of fighting them.