Every tier includes all 9 model families. Pay for throughput and monthly volume, nothing else.
Yes — a cstm_lm_* key only authorizes CareerLM endpoints, a cstm_em_* key only authorizes CareerEmbed, and so on. This scoping means a leaked key for one family can't touch the others. Generate one key per family you actually use.
Yes. Your CSTM-2 developer plan is a completely separate subscription from any consumer CareerStudioMax plan you might also have — different billing, different Stripe subscription, upgrading one never touches the other.
Requests beyond your monthly quota are rejected with a clear error until the quota resets or you upgrade — never silently throttled without telling you.