The docs for nh3.clean() list filter_style_properties as a supported keyword argument. However passing this argument raises an error:

clean() got an unexpected keyword argument 'filter_style_properties'

Inspecting the runtime signature confirms it is not implemented:

(html, tags=None, clean_content_tags=None, attributes=None, attribute_filter=None,
 strip_comments=True, link_rel='noopener noreferrer',
 generic_attribute_prefixes=None, tag_attribute_values=None,
 set_tag_attribute_values=None, url_schemes=None)

So filter_style_properties not available, along with allowed_classes it appears.

As a result, you can enable inline styles but cannot safely constrain them.