The media manager currently only supports public and s3 disks. Make sure you have the correct config set in your .env file.
In the neutrino config file you can adjust the resize amounts.
'media' => [ 'image_sizes' => [ 'large' => 2000, 'medium' => 1200, 'small' => 600, 'thumb' => 280, ], 'thumb_crop' => 'square', ]
You can also add you own custom sizes. The values are in pixels.
The thumb_crop value is square for a centered cropped square image. Rename it to anything else for normal resizing.