Email for sensitive taks, anonimity. Just toregister to services and never use again. but good if comes with good security and privacy also.
If you want an account not linked to your identity to sign up for accounts also not linked to your identity. To create spam, fake or throw away accounts on other services, any email provider will do. Some do a form of KYC, but it’s lackluster in most cases. Popular providers for “normal people” like Yahoo, Gmail and Outlook are great, when you want to keep a low profile registering for services with your “anonymous“ email address.
Of course you have to sign up and sign in using an VPN or Tor.
Please don’t do illegal stuff and especially don’t bring harm to others.
It depends on whether you need to maintain access to the address.
Temporary addresses are probably more anonymous. But are treated with very significant suspicion as a result. Which often means anything you try to do will just get blocked.
If you need to maintain access to the account I’d probably go with Tuta or Proton leaning more toward Tuta which doesn’t support recovery contact details.
Do bear in mind that both of them will enforce all legal orders and that there are very much limits to how much privacy and anonymity you can actually get when using email.
Email is also very commonly abused for things like spam and these companies have to take such abuses seriously or risk getting the entire company blocked by other email providers.