Depends on how much you trust IBKR. If you open IBKR LLC (us version) SIPC protection is up to USD500,000. If you open say UK version like me, then it's GBP75,000. But I am too lazy to switch to LLC (US version). It is like FD and bank acocunt. Some people want safety so max only RM250k.

Otherwise if you don't mind about SIPC protection then no limit.