Get dynamically created image URL in a block with paragraph and media bundle
I wouldn't try to hack the render array content. You might be more successful with the paragraph entity:

{% set uri = paragraph.field_slide_image.0.entity.field_image_upload.entity.uri.value %}

{% set url1 = uri|image_style('style1') %}
{% set url2 = uri|image_style('style2') %}
{% set url3 = uri|image_style('style3') %}


For the filter image_style install the module Twig Tweak.