This is not so much as a question, but just something I wanted to share, since it took some work for me to figure it out.

When creating new groups programmatically, one can set the default permissions, but they are somewhat cryptic, and not that intuitive.

Here is the list of default permissions for Groups (these will give access to specific features)

User Group Permissions

Cultures and Hostnames (I)
Public Access (P)
Rollback (K)
Browse Node (F)
Create Content Template (ï)
Delete (D)
Create (C)
Publish (U)
Permissions (R)
Send To Publish (H)
Unpublish (Z)
Update (A)
Copy (O)
Move (M)
Sort (S)

so, in order to use these in your code, do something like this:

First create the IUserGroup

UserGroup group = new UserGroup
        {
            Alias = "mycustomgroup",
            Name = "My Custom Group",
            Icon = "icon-umb-members",
            Permissions = new List<string> { "I", "P", "K", "F", "ï", "D", "C", "U", "A", "O", "S" },
            StartContentId = 1080,
            StartMediaId = 1081,
            Key = Guid.NewGuid()
        };
        group.AddAllowedSection("content");
        group.AddAllowedSection("media");

Then create the group in Umbraco

public UserGroup CreateUserGroup(IUserGroup group)
        {
            UserGroup newGroup = (UserGroup)userService.GetUserGroupByAlias(group.Alias);
            if (newGroup != null) throw new Exception("Group already exists");

            try
            {
                userService.Save(newGroup);
                ConnectorContext.AuditService.Add(AuditType.New, -1, newGroup.Id, "User Group", $"User Group {newGroup.Name} has been created");
                return newGroup;
            }
            catch (Exception ex)
            {
                logger.Error(typeof(UserGroupHelper), ex.Message);
                logger.Error(typeof(UserGroupHelper), ex.StackTrace);
                throw;
            }
        }