regarding W3 Total Cache settings

Hello, just activated W3tc on my wordpress and seems working fine. just need some expert opinion which options i need to set which i must not… currently its running under default configuration. and here’s the compatibility log

Server Modules & Resources:

    Plugin Version: 0.9.4
    PHP Version: 5.5.9-1ubuntu4.4;
    Web Server: Apache
    FTP functions: Installed (required for Self-hosted (FTP) CDN support)
    Multibyte String support: Installed (required for Rackspace Cloud Files support)
    cURL extension: Not installed (required for Amazon S3, Amazon CloudFront, Rackspace CloudFiles support)
    zlib extension: Installed (required for compression support)
    Opcode cache: Not installed
    Memcache extension: Not installed
    HTML Tidy extension: Not installed (required for HTML Tidy minifier suppport)
    Mime type detection: Installed (Fileinfo) (required for CDN support)
    Hash function: Installed (hash) (required for NetDNA / MaxCDN CDN purge support)
    Safe mode: Off
    Open basedir: Off
    zlib output compression: Off
    set_time_limit: Available
    mod_deflate: Installed (required for disk enhanced Page Cache and Browser Cache)
    mod_env: Installed (required for disk enhanced Page Cache and Browser Cache)
    mod_expires: Not installed (required for disk enhanced Page Cache and Browser Cache)
    mod_headers: Not installed (required for disk enhanced Page Cache and Browser Cache)
    mod_mime: Installed (required for disk enhanced Page Cache and Browser Cache)
    mod_rewrite: Installed (required for disk enhanced Page Cache and Browser Cache)
    mod_setenvif: Installed (required for disk enhanced Page Cache and Browser Cache)

Additional Server Modules

    New Relic
    PHP version: Not supported: 5.5.9-1ubuntu4. Supported versions are 5.2.x, 5.3.x, 5.4.x.
    Operating System: Supported
    Web Server: Not Supported. (Apache See NewRelic Requirements page.)

WordPress Resources

    /var/www/.htaccess: OK
    /var/www/wp-content: OK
    /var/www/wp-content/uploads/2014/11: OK
    Fancy permalinks: /%postname%/
    WP_CACHE define: Defined (true)
    URL rewrite: Enabled
    Network mode: No

somebody please explain these 3 option

HTML Tidy extension: Not installed (required for HTML Tidy minifier suppport)
mod_expires: Not installed (required for disk enhanced Page Cache and Browser Cache)
mod_headers: Not installed (required for disk enhanced Page Cache and Browser Cache)

are they very useful? if yes how can i install them? i’ve install wordpress through ubuntu 14.04

regards,