VPN's -- All are not created equal, first and most important you want a VPN that does not create or store any logs. This is only an example. not endorsing any products, PIA vpn has multiple servers and does not (at least last time I checked) save log files, compared to a service like Avast's antivirus program and their VPN which retains log files. So while you might surf anonymously using certain VPN's ,when push comes to shove, log files kept by certain VPN's can be obtained and used against you. So choose wisely.
2nd consideration -- Myself included, most have probably signed up using your common email address, so you are trackable that way. Recommendation is to use a service like Pronto mail (again an example no endorsement ) and I think they may still offer some free accounts, and then use that email address to sign up for sites like this.
Problem with VPN's, some web sites use software that looks at your IP address and if it comes from an VPN service (and other sources) that will not allow you to connect - So if you have a VPN and cannot log into certain sites, you will probably have to disable your VPN to gain access to certain sites.
Last, it's still all 0's and 1's so nothing is foolproof.