Hi,
A. Why not keep multiple fields in the base tab or first tab? You can rename it what you want.

1. Xprofile Location:- We will check for compatibility and will let you know by early tomorrow.
2. Conditional Profile field plugin’s latest version is not tested with the Ajax Registration plugin. We will need a little time on that to test for the compatibility.
3. You can diable auto activation mode by adidng this code

add_filter( 'bpajaxr_is_auto_activation_mode', '__return_false' );

4. Privacy settings:- You can control it. The default applies to newly registered members. If you allow users to change it, They can control their profile visibility or you can disable for user and manually set for individual users.

I can assist with the code quickly, I need one last answer from you:- Do you want to keep pagination for the 100 users? Here is for with pagination

/**
 * Only show recent 100 users.
 *
 * @param array $args query args.
 *
 * @return array
 */
function buddydev_limit_las_100_members( $args ) {
	$args['max'] = 100;

	return $args;
}
add_action( 'bp_after_has_members_parse_args', 'buddydev_limit_las_100_members' );

5. Sorry, there is no special css for it. You may want to customize the ajax-register-form.php file instead by copying it to your theme.

Regards
Brajesh

Hi Julia,
Thank you.

4. I am a bit worried about applying the per page setitngs but here we go with teh modified version.

/**
 * Only show recent 100 users.
 *
 * @param array $args query args.
 *
 * @return array
 */
function buddydev_limit_last_100_members( $args ) {
	if ( bp_is_directory() ) {
		$args['max']      = 100;
		$args['per_page'] = 100;
	}

	return $args;
}
add_action( 'bp_after_has_members_parse_args', 'buddydev_limit_last_100_members' );

Please remove the previous code and use this. It may affect widgets in the directory sidebar too(Earlier code did too).

5. Please open bp-ajax-register.js and change the value ‘1000’ to some other value. The 1000 means 1 second(It is in ms). So, if you want it for 1.5 second, you can put there 1500. Please do note that the changes will be lost in next update.

Regards
Brajesh

4. So, I am assuming that it is fine for your use case as there are no user widgets for the directory sidebar.

For 3rd, Please try again. It should work and disable the auto activation of user acocunts.