Outlined below are the different settings in the admin panel under "Site Settings", and if you change them, what will occur.
Modify this to change the name of your site, including in the <title> tag, the maintenance page and some system emails.
Use the Google Recpatcha to protect yourself from spam registrations and logins, and to verify the legitimacy of a users session. You can set this to Enabled for Registration and Logins, or just Registrations. Default: Disabled.
Enable or disable the built in messaging system which features Mass Messaging, user-specific messaging with replies in thread format and email notifications. Default: Disabled.
What do you want to echo when you use the echouser function? You can use this to echo their name in several different formats. Need their username instead? Use echousername. If it cannot find the user, it will echo "Deleted". Default: FName LName.
This does what it says. If you want to disable the Editor, you can change this. This is used in the messaging system. Default: Enabled.
Don't want anyone accessing your site insecurely? Enabled this. This will redirect any users from an HTTP (non-secure) connection to HTTPS. Make sure your SSL Cert is valid before doing this! Default: No.
This will change the force_pr value in your users database for all users to 1, requiring every user including the current one to reset their password. They will not be able to leave the user settings page until this make this change. This will always be no, however when you change it to Yes and save changes, it will perform the above action, and reset back to no. This isn't a setting, but a function.
This will require users you make from the admin panel to reset their passwords by default. If you enable this, the force_pr value in your users database for this user will be 1 when created. Default: No.
Need to go into Maintenance Mode to do an upgrade? Enable this! This will display a "Maintenance Mode Active" message for those in the default Administrator permission group (ID: 2) and redirect the remaining to the maintenance page. This will occur until the setting is disabled. Default: No.
Want details on how many visitors are visiting your site? Keep this on! Site getting laggy, stumbling and having issues? Disabled this to see if it fixes it for higher volume sites. Default: Yes.
This allows users to receive email notifications for new messages if they are subscribed via their settings (by default they are). Only enable this after your email settings are done! Default: Disabled.
Use this as a safeguard to only allow users to add/remove permission levels they have access to. You might use this in a format to give certain users access to add/remove users or make site changes, but you don't want them to give other users permissions they don't have, or take those away. Your safeguard for this (in your own case if you have certain permissions not assigned to yourself) is by restricting admin_pages.php and admin_page.php to the default Level 2 as you can do anything from these pages currently. This will still show the user the levels on admin_user.php but will have a disabled attribute. Default: Disabled.
Only allow one permission level per page using this setting. This is particularly good for ensuring no overlap in permission levels. You can have a permission group hierarchy such as this:
In this case you want to give all your User Managers access to admin_user.php and admin_users.php, and yourself of course, but many not to those who manage your database only (maybe you want to give them access to site and email settings only). In any case, it will change the checkboxes on admin_page.php to radio buttons under Add Permission Level and restrict addition from admin_permission.php to be added only if no other level has it. Default: Disabled.
Don't want users to choose their usernames? No worries! Enable this and a users default username will be their first initial and last name. This already exists? Okay! Lets do first name and last initial. Still not good? Email address it is since you won't be duplicating emails in your database! This will remove the username field from both the external and internal registration forms. Default: Disabled.