Forgive me, I'm not a network guy and would like to know which of these can I use that will allow me to use the wireless "key" or "passphrase" that came with the stock router. Or, if that isn't possible then the encryption that allows alphabet (Latin or English) and numbers.
I guessed as much, which is why I gave the most suitable answer without bombarding you with surplus information.
But three options is too complex?
WPA2-PSK is the strongest password-based encryption among those choices. Use any character from 8 to 64 charcers. You can use, letters, numbers and symbols.
Force CCMP (AES) is the strongest cipher available among those choices. It's harder to break than TKIP.
Enable key reinstallation addresses a weakness in WPA and WPA2. WPA and WPA2 have a fundamental flaw in them, and this provides a workaround.
Set those three as indicated and you'll have the strongest password-based wireless encryption currently available on that firmware. It's not perfect, but someone would have to put in a lot of effort to break it.