Using iphone SE2 with Apple Watch 8

These features are available on an Watch set up for a family member who doesn't have an iPhone;

• High and low heart rate notifications are available for users 13 and older.
• Heart Rate Variability (HRV) is available for users 18 and older.
• Fall Detection is available for users 18 and older.
• Users under the age of 13 can use move minutes, rather than active calories, for their Move goal in the Activity app.

None of these features and apps are available on a phone set up for a family member; Medications, respiratory rate, irregular heart rhythm notifications, ECG, AFib History, Cycle Tracking, Sleep, Wrist Temperature, Blood Oxygen, Walking Steadiness, Audiobooks, Remote, News, and Shortcuts.

Set up Apple Watch for a family member - Apple Support

M1 Mac mini, macOS 13.5;  Watch, series 7 GPS/cellular, watchOS 9.6; iPad Pro 2nd Gen, iPadOS 16.6; iPhone 12 Pro, iOS 16.6; TV 4th Gen, tvOS 16.6; HomePods, audioOS 16.5 and Airport Express w/ Airplay 2

In the link I provided it states that it is preferred that the Watch is a cellular version. A data plan for a watch is usually $10 to $15 a month added to an iPhone's cellular service plan.