kelcells, were the Vanilla GCs you bought MasterCard or Visa?
Based on my receipts, it kinda looks like MasterCard GCs count towards Wellness+ Gold status, and Visa/AmEx GCs don't.
For the 20% off with Gold, note that it gives you the lower of the current sale price and 20% off the regular price. So if you only buy items on sale, you might not benefit much from the 20% off.
One nice thing about the Plenti points is that they expire after 2 years, which is much longer than competing drugstore programs (CVS/Walgreens). (CVS in my area was previously nicer, taking expired CVS coupons/extrabucks, but they've pretty much stopped doing that.)