For me:
- this opinion is different from mine, but I respect it: ignore
- this opinion is different from mine, and I do not respect it (e.g.: racism): downvote
- this opinion is spreading misinformation: downvote
- this comment is an insult to someone, regardless on whether it was "deserved" or not (e.g.: "this is a stupid question"): downvote
- this comment is breaking community rules: downvotes
For the small tabs, you may try to enable custom stylesheet (userChrome), there are plenty of themes on the web, but if you're looking for something more specific you may edit it yourself, it's very easy. Oh and the default start page is pretty ugly I agree, there are plenty of alternative start pages on the add-on store For the data collection, firefox forks like librewolf should have that disabled by default (I don't have any experience tho)