Brave Browser introduced tor integration for private tabs. https://twitter.com/brave/status/...
Is security taking a toll when Tor network is accessed through not the actual Tor browser?

Well, it CAN be.

If Brave does it the right way, then it should be mostly the same as using the Tor browser.

The reason why the Tor project wants you to use their browser is that there's tons of ways that site developers have figured out how to track people besides their IP and cookies - things like the browser window size, User-Agent, traffic patterns all go into a heuristic nowadays to determine the likelihood that user X has identity Y. On top of that, JS and browser plugins are security nightmares.

The Tor browser developers have done a good job of mitigating those risks, but I can't really say whether this is applicable to your situation or whether Brave's implementation is secure enough.