

Generally you post onto the public “federated” timeline. With Mastodon this timeline contains posts from many different Mastodon servers that are all federated with each other, but it appears as one single timeline.
Hashtags are really central to the Mastodon experience. There is no algorithm that automatically suggests posts and accounts like on mainstream centralized services. Instead you gotta purposely use hashtags to discover posts and people. Add descriptive hashtags to your posts, the more the better. This helps people searching for specific topics find your posts.
You can follow people and they can follow you. Posts from people you follow will appear on your home feed. You can also follow hashtags and posts containing those hashtags will appear in your home feed. At the moment there’s no official support for communities like with Lemmy; following hashtags on topics you like is the closest you can get to that functionality. (You can also make separate lists of hashtags outside of your home feed).
The people and interests on Mastodon has a lot of overlap with Lemmy.
Here are a couple of resources you might find helpful: https://fedi.tips/ https://fedi.directory/
Conservatives will think the same about any public figure who’s any degree to the left. It’s just a human cognitive bias at play that we’re all susceptible to. If you think someone is a shitty person, that’s going to cause you to overemphasize whatever physical features you find negative about them. The danger of this is that you might in turn start using those negative features as an unreliable heuristic to judge the character of other people before you even get to really know them.
The different fashion/makeup trends among people across the political spectrum can also come into play similarly.
There are conventionally unattractive public figures on the left too, but if you know beforehand that they’re on your “team”, you probably won’t even take particular notice to these “defects”. In some mirror universe where MTG was as far left as AOC, you’d probably wouldn’t think she looked “evil”.