Do not download anything off of the onion network unless you have dozens of reliable sources telling you it's safe. There is really only one reason to ever put something up for download on the onion network, and that is because its illegal (be it leaked government documents, cp or credit card numbers, they're all illegal).
And even if things are downloaded from the clearnet, having links to it from the onion network is also a really big red flag - so unless links to it exist on the clearnet, too, I wouldn't.
I am a big believer in using TOR to browse the regular net, though, so if that's a possibility, you should definitely do it.
As for using VPN, is basically a waste of time if you are using TOR. Using a VPN means you are connecting to the internet through another computer (at its core) and usually transmitting the data in encrypted form back to your computer. This means that your ISP cannot see what you are browsing, or that you even are browsing. The VPN can, though. TOR is essentially a series of VPNs connected together in a format that makes it impossible to track where, how, and what data is being transferred between them to anyone outside the sender and receiver (and even they can't tell where exactly that data is going to end up). Your ISP can see that you are using TOR, but it cannot see any of the data you send or receive (because just like with the VPN, the data is encrypted). By using a VPN together with TOR you are just creating another node in the system, not really making it any more secure (but usually making it a great deal slower).