In practice, you’re almost certainly not getting faster netflix or youtube by adding an extra VPN into the congestion path. There are some weird edge cases where particular peering agreements and anycast routing quirks leave some exceptions to that, but I highly doubt a non-negligible amount of users are actually seeing a consistent speed increase on a VPN, and the vast majority would definitely see a decrease. That VPN is doing more to interfere with traffic than an ISP is.

As for tracking you and selling your data, I trust my ISP to behave better in that regard than I do some shady VPN provider. And I don’t even trust my IP that much.