Can I create second Apple Account for my Apple Watch?

1. You can, but why?
2. If you make your Apple watch have a different Apple ID than the iPhone then you will need to use Family Setup to set up the watch and there are several restrictions when that is done. click here ➜ Set up Apple Watch for a family member - Apple Support
   1. The following features and apps are not available (with Family Setup): Medications, respiratory rate, irregular heart rhythm notifications, ECG, AFib History, Cycle Tracking, Sleep, Wrist Temperature, Blood Oxygen, Walking Steadiness, Audiobooks, Remote, News, Shortcuts, and the double tap gesture.
3. Your iPhone and Watch would not be linked, so calls, messages and notifications would not be shared with the Apple Watch. Apps would need to be repurchased for the Watch specifically, and iTunes media and subscriptions would need to be reacquired with the Apple ID used for the watch to have access to them, or use Family Sharing to share them with the watch.
4. Its very complex to do this, and unless there is a very good reason to have them have separate Apple IDs, there's nothing to be gained by it if the watch is only used by one person.

For multiple people then Apple Watch Family Setup is suggested so each person has their individual device with their individual Apple ID.

For iCloud Storage, you can use Family Sharing to share it across different Apple accounts. There should be no issue with that.

click here ➜ Share iCloud+ with your family - Apple Support

I agree with Phil0124.

It's masochistic, don't do it.