SFC II OP cloak is designed to reduce/eliminate damage from incoming direct fire weapons.. and to break/ lose lock on from seeking weapons and to prevent seeking weapons from being fired on you when you are cloaked.. plus the improvements on it are that you can now cloak when tractored and also it uses a new damage chart for weapons hitting you. Cloak in OP is beefed up, however an invisible Cloak in Starfleet Battles was an optional rule that people could play with on the board game, however it was elected to stick with the stock rule set for cloak in SFC, SFC II EAW and SFC II OP. that is.. Non invisible cloak with an ability to lose lock of seeking weapons, prevent seeking weapons from being fired on you, and to reduce/eliminate damage taken from direct fire weapons, cloak when tractored, etc...
Hidden cloak is a TV feature and is not a common rule of SFB or SFC, with exception of SFC 3.