Tor browser is designed exactly for this purpose.
Unlike a VPN, which alone is really only useful for providing confidentiality and integrity between you and your ISP (e.g. when using hotel WiFi), Tor is designed explicitly with anonymity in mind. It is easy to use and free, and provides an extremely good level of anonymity, which is perfect for research of illegal or questionable material. Using it is most certainly not overkill. It is a good idea.
VPNs have a nasty history of recording browsing history even when they say they don't, and revealing the logs to law enforcement when they request it. Tor, which connects to a website over three random relays, is designed such that no individual relay is able to simultaneously know both who you are and what website you are visiting. This is what provides such a good level of anonymity.