partial protection inside free accessable blogposts

1. Is WP-Members able to handle protected Podcast feeds? (using “Blubrry PowerPress”)

It depends on the setup. But in general, I’d say no. If it’s really a “podcast,” then restricting it is not part of what podcasting actually is. You could conceivably restrict the feed, but then it’s no longer a podcast, but just streaming audio/media, and filesystem restriction is totally different than content.

2. Is it possible to protect only single partial sections inside a Post? In example with a surrounded shortcode?

Yes. See: https://rocketgeek.com/plugins/wp-members/docs/shortcodes/status-shortcodes/