There are only two picture size loaded

Hi eatlikej. The default image sizes of WordPress are “thumbnail”, “medium”, “large” and “full” (the size of the image you uploaded). These image sizes can be configured in the WordPress Administration Media panel under Settings > Media. This is how you can use these default sizes with the_post_thumbnail():

the_post_thumbnail( ‘thumbnail’ ); // Thumbnail (default 150px x 150px max)
the_post_thumbnail( ‘medium’ ); // Medium resolution (default 300px x 300px max)
the_post_thumbnail( ‘large’ ); // Large resolution (default 640px x 640px max)
the_post_thumbnail( ‘full’ ); // Full resolution (original size uploaded)

The Hueman theme creates the following thumbnail sizes when an image is uploaded:

add_image_size( ‘thumb-small’, 160, 160, true );
add_image_size( ‘thumb-standard’, 320, 320, true );
add_image_size( ‘thumb-medium’, 520, 245, true );
add_image_size( ‘thumb-large’, 720, 340, true );

The first thing I would try is to install and run the Regenerate Thumbnails plugin. That should recreate the above size thumbnails for each image currently in your Media Library.

Is this something to do as I have EWWW Image Optimizer installed already?

The two plugins serve different functions. One optimizes the images, the other regenerates the images based on the image sizes registered in WP and the theme.

Is this the future of regenerate Thumbnails?

No, this is a WP feature, not related to the plugin.

Is it absolute necessary to have regenerate Thumbnails??

No, you don’t need the plugin in order to use the theme.

Another option you could try is Simple Image Sizes.