And which one should I use?

What’s the difference between Options API and Setings API?

I have a theme with over 100 admin options, how should I register & store them? At this moment I’m using Options API but I’m not too happy with it, every single option is being registered separately so they create a lot of database queries.

I see three ways of storing WordPress options/settings at the moment:

1. Options API – the old (the worst?) way.

(I’m using this one already)

<form method="post" action="options.php">
<?php wp_nonce_field('update-options'); ?>        

// all the inputs

<input type="hidden" name="action" value="update" />
<input type="hidden" name="page_options" value="option1,option2,option3,..." />
<p class="submit">
<input type="submit" value="<?php _e('Save Changes') ?>" />
</p>
</form>

And then in the front end:

echo get_option('option1'); 

Looks ugly and I don’t think that’s the right way of storing big number of options (I’d love to group them somehow).

2. Options API – 1 option as a big array.

I’m not sure here how to update this array using html forms, anyone?
I believe it should go like:

$opt['option1'] = foo
$opt['option2'] = foo
$opt['option3'] = bar

update_option('theme_settings',$opt);

And then in front end:

$settings = get_option('theme_settings');
echo $settings['option1']; 
echo $settings['option2']; 
echo $settings['option3']; 

I’ve heard it really decreases number of queries and I have them all as one option. I’d love to use this one but as I mentioned above I’m not sure how to update this array of options within WordPress admin form. I guess: <input type="hidden" name="theme_settings" value="option1,option2,option3,..." /> will overwrite the array instead of adding new elements?

3. Settings API – the new way.

Requires a lot of additional code:

function register_theme_settings() {
    //register our settings   
    register_setting( 'theme-settings', 'option1' );     
    register_setting( 'theme-settings', 'option2' );     
    register_setting( 'theme-settings', 'option3' );     
    register_setting( 'theme-settings', 'option4' );     
    register_setting( 'theme-settings', 'option5' );     
    // imagine this for 100 and more options    
};

And I’m not sure what’s the difference between this and the method with one option as an array?

tl;dr So, how should I project my theme settings storage so it will be working fast and store all the options/settings in one place so I will be able to, for example, echo/dump them all with one simple function (yes, I want to do that badly but I have no idea how to do that with this Settings API). The second method looks the best so far.