Firefox having an empty check box on Blocks cross-site trackers is a lie.
Docs Enhanced Tracking Protection in Firefox for desktop
Ignoring isolation is misleading - in this marketing context a plain lie.
They could have made a differentiation between all-blocked vs some-blocked, but empty indicates none are blocked, which is a lie.
I wouldn’t use it.
Seems to me like free plan is what browsers natively support anyway. (Scam site blacklist. I highly suspect they use the same. They can’t compete with the one Google hosts and all major browsers integrate.)
And instead of paying 15 usd per month, Windows defender is a well funded, well established, well trusted solution.
There’s no practical gain in blockage before download. Windows defender scans upon and after download, before execution.