Best practice - never share the Hosted Feature Layer.
Create Hosted Feature Layer View(s) from your original layer. Turn editing on/off on the View. Add the View to the map. Share the map and View to the group. Repeat as required.
e.g.
- My_Layer - not shared
- My_Layer_View1 created. Editing enabled and added to Map 1. Map 1 and View 1 shared to Group 1.
- My_Layer_View2 created. Editing disabled and shared to Map 2. Map 2 and View 2 shared to Group 2.
This way you can always control who has access to your data. Views let you filter, turn on editing settings (add, update or delete) and you can even disable editing on select fields.
Sharing the original feature service is not great as you lose all your options. You can't open/close doors to people when everyone is in the room already.
https://doc.arcgis.com/en/arcgis-online/manage-data/create-hosted-views.htm
https://www.esri.com/arcgis-blog/products/data-management/mapping/getting-started-with-hosted-featur...