Can I store Apple Watch for 2weeks and not be on the charger

Apple recommend devices to be charged to 50% for long term storage and new stock usually comes from Apple charged to that level.

Short term you can charge it fully.

I would add that if a charged lithium battery discharges itself completely in 2 weeks while the device is powered off then the battery is faulty.

Just charge it up then shut it off and I'm very certain that it would last well beyond 2 weeks ;-)