Is it less or more safe to login to personal accounts (email, Amazon,
etc.) when using Tor, compared to not using Tor?
Generally speaking: Less safe. Don't do this.
When using Tor, an exit operator can steal your account credentials if you log into a site without using a TLS connection. However, even if your browser does indicate that you're using HTTPS, this doesn't necessarily mean that your credentials are safe. Many websites use mixed content (some content is encrypted, some isn't). If some of that content is also on the same domain as your encrypted / authenticated connection, it can leak your cookies (most browsers won't warn about mixed content, or will warn you but establish the connection anyways, meaning your data has already leaked). Blocking mixed content and always logging in over HTTPS can help prevent this.
However, logging into anything essentially defeats the purpose of Tor. By logging in you are confirming to the service operator (and anyone else who can tell you've logged in) that you are the person with that account, effectively de-anonymizing you. Depending on your risk tolerance, what the account is (and what information it has on you), what threats you're trying to prevent, etc. this may or may not be a problem.
TL;DR — it all depends what you want. If you want anonymity, Tor may help to a certain degree, but will be worthless without following general opsec practices. If you're just trying to protect your account credentials: Tor at best is neutral, and at worst may bite you.