don’t put all your eggs in one basket

That's a good approach - but there's a better one. If at all possible stick to software that uses standard data formats and is able to interact with other software. For example Lemmy uses Markdown (a standard) and it can interact with other software (on the fediverse).

If we ever decide to stop using Lemmy, there's a good chance all of the valuable content we're writing — like this discussion — will live on in whatever other software we decide to switch to instead of Lemmy. Because being Markdown, it's easy to import, and being on the fediverse, it will be easy to transition to a replacement gradually over time with the new software and lemmy both being used at the same time during a potentially years long transition period.

Unfortunately I don't know of any (good) web browser that does that. It's certainly possible for bookmarks/tabs/settings/etc to be synced between browsers, but in general browsers only ever support once off imports, they never actively maintain a shared set of data between browsers.

But there's an out — extensions. For example I don't use the password manager built into my browser. I use a browser extension for passwords and my password manager has an extension for all browsers. Obviously as locked down as passwords need to be, I don't want my passwords accessible outside that app/those extensions, but it does have a good import/export feature and I have used it to test other password managers. I should really look for a good extension that manages bookmarks well and syncs them between browsers.

I were on Apple, I would be using Firefox

I dunno if that's true. There are some really good browsers on the Mac that I suspect don't run (or don't run well) on whatever operating system you do use. Access to awesome Mac only software is the reason I use a Mac, even though I don't particularly like the company Apple has become (they were a wonderful company 20 years ago in my opinion).