Same issue here. Apple Watch 6 Cellular. Took a good hit on battery performance going to 7.3, could go all day, and a full night sleep, and be at 30% in the morning. Now I’m down in the teens before bed, and have to charge before bed or won’t make it through the night. Just upgrade to 7.3.3, and it has gotten even worse. Charging in the middle of the day now.
Hoping for a fix to this ASAP!