Brave does support opening tabs from other devices, sync works good so long as it always has at least 1 device in the sync chain, so if you only have 1 device and have to reinstall it the settings might be lost, but if you have 2 devices and reinstall one the settings are still saved whenever you rejoin the chain. The reason is there are no accounts saved in brave, so the only way to ID your browser is by the sync chain. If the sync chain has no devices it may be removed from the sync servers.
All of the crypto rewards stuff can be disabled with 1 switch, and a second switch if you also want to turn off wallet, but it’s not really active unless you configure it. Rewards is there as a way for them to make money without having to make Google or Bing the default search engine as other browsers do.
Brave is a great browser, but Firefox is also great and very configurable. And thanks to this thread I learned that FF’s interface can be customized, which was one of my main reasons not to use it anymore. I’ll play with it again, it’s important to have a non-chromium based browser as an alternative.
If you just want to join an instance, it doesn’t really matter if they are running Mastodon, Pleroma (or one of the forks), you will be able to follow and interact with everyone else on the microblog portion of the Fediverse. In fact from a Kbin instance you can do Lemmy communities and Mastodon microblogging from the same platform (Kbin calls communities Magazines and in the magazines are Threads, and they call the mastodon-like portion is just called microblog).
If you want to self-host your own instance, then you need to pay attention to the difference in the platfoms, Pleroma is lighter, Mastodon is more modular, and there are many forks of both each with their own strenghts and weakenesses.
If you don’t like the frontend, you can use Elk, or Soapbox, or some others out there, as well as all the apps and PWAs for either platform, most are compatible with both.