About to Dryhop, does fermentation have to be complete?

Hey guys
First time brewer, long time beer fan here...
I was about to transfer my beer from my primary to my secondary when i noticed a bubble form in the airlock. Do I need to wait until its 100% fermented before I transfer? There's no more krausen and it's been about 6 days since i pitched the yeast

Do not transfer to secondary until fermentation is complete. The only way to know is to check gravity a couple days apart to make sure it is the same. And depending on the type of brew, maybe skip secondary all together. It is often not necessary.

Personally, I rack to the secondary Before the bubbles stop. The reasoning is to get off the trub and leave some residual CO2 production to help flush out any oxygen in the headspace.
I sometimes rack to a Carboy if I want perfectly clear beer but mostly I rack to a corny keg and release the pressure daily until there is no more gas produced. Then I pressurize the keg to get the volumes of CO2 I'm shooting for.
So, rack on the scheduled day and record your SG. This info will help you later.

Dryhopping during fermentation means that those awesome hop aromas will blow off with the co2 during fermentation. I dryhop in the primary, but I wait until 5 days before packaging before dryhopping. Once fermentation is complete, and the beer is clear, I dryhop and wait 5 days and then package.

Oils from the dryhops will cling to yeast, so dryhopping during active fermentation is a bad idea for those two reasons. (The hops oils will cling to the yeast and fall out when the yeast flocculates, plus any hops aromas will blow out with the co2).

A bubble in the airlock does not mean it is still fermenting, a whole host of things can cause bubbles to pass through the air lock.

Maybe I should have added that I also do not dry hop until it is finally in the keg and about 5 to 7 days before serving.