If I use Instinctive Strength Unity and Instinctive Dexterity unity in (Lunar) combat, am I correct that by spending 8m each on them that I can use the 3rd Excellencies for STR and DEX to double my attributes at appropriate instants?

I have Claws of the Silver Moon and I'm pretty excited about the prospect of doubling my damage and accuracy modifiers. Could I also use other excellencies to add more dice (or successes)?

I'd love to have someone explain in which situations (in general) it is more advantageous to use 1st, 2nd, and 3rd Excellencies for maximum effect.