Connector current/thermal rating
Molex makes a vast selection of connectors each which have current ratings. So I’m not going to pick one out for you. Rather, I’ll give you a general design philosophy on connectors, but Molex does have a current ratings if you can find the specification on every connecter or contact.

But the so called “Molex 4 pin HDD connectors” in PC’s were rated for 10A with separate return contacts for +5V and +12V  . 

Generally look for this type of pin in cylindrical sleeve socket for high currents and not simply bifurcated (split or double point ) contacts that have small surface area contact.  High wetting current contacts >2A are never gold plated while those for &lt;=2A are generally gold plated with varying quality for gold thickness. 

The same is true for all Relay contacts except they use a silver palladium alloy while connectors are generally plated with lower cost metal alloys such as nickel or zinc over steel , brass or beryllium copper for substrate.