Binance type high-rank exchanges good enough security
Slightly mistaken there, high rank exchanges also are the biggest targets since the hackers know that they are going to get the biggest market share of users accounts there. Same with high ranked torrent sites and file sharing sites. Thus it makes sense to have accounts on more than one exchange as failsafe in case one gets hacked and you need to trade still.
Again dont keep trades on standby on exchanges, which seems an illogical thing to do since you are there to trade anyway but it is a safety thing, you just have to trust and hope the exchange does not get hacked in the meantime while your money is blocked on the orderbook.