I know in tournaments you must have official pilot and upgrade cards on the board, and you need the exact number that you're using (eg: using four cluster missles on four ships).

In tournaments, do you also need the Reference cards present for any abilities, bombs, or secondaries? If you don't have the Reference card on the table are you not allowed to use that weapon/ability?

The only requirement is the pilot and upgrade cards and the correct tokens. Reference cards aren't a necessary requirement, but always handy to have.

Or just one BIG one.

Its nice to have the reference cards, but you dont have to have them. If there is a question, that is what the TO is for.

They'd fall under the same heading as having the rulebook and FAQ when you play. You may not need them but if there is a dispute you may have a harder time proving your case without the reference available.