[sinisterlee]

You recommend tor browser over a built in option like in brave browser?

You never know what type of Information Brave collects, hence direct access via the Tor browser Is always the better option.

What are your opinions about brave browser and firefox private?

Do note that private/Incognito In Firefox, only relates to your local environment and not your online activity.

Do you consider startpage.com to be private at least for personal usage?

It's much of a muchness to most other private search engines.

Personally, I prefer MetaGer. It also allows you to open webpages via Its built-In proxy.

Rarely seen startpage mentioned, duckduckgo seems to be mentioned a lot by Americans particularly.

DuckDuckGo seems to be the most popular.

Makes sense, using the tor browser adds another level of seperation.
Got two more points to add to your list.
Use a device exclusively for your grey activity and also obsfucate your internet connection, don't use home wifi if possible.