Browsers on iOS may be using the same rendering engine under the hood but they make different decisions for UI or how certain features work. They can be useful if you don’t like the decisions Apple made with Safari.

An example of a decision Safari made that I don’t like: if you open too many tabs you reach a limit, but it doesn’t tell you that and just silently overwrites other tabs you have open.

My assumption would be for account syncing.

I use Safari, but whenever I go on a pilgrimage to try a different browser, I also get it on my phone so I can access tabs and bookmarks whenever I am.

For syncing from desktop chrome probably