Maybe I’m misunderstanding but if I login to a different Gmail account, it logs me into the same account everywhere in the same browser. That includes calendar, YouTube, everything. Google uses single sign-on for all their apps.
You can use multiple Google accounts in the same browser by using the “Add Account” feature—click the account button (it’s your profile photo) in the upper right corner of Gmail, then click the “Add Account” button. This will open a new tab where you can sign into the other account.
After you’ve done this, your accounts will be linked and you can toggle between them using the account button.
I also have a free fastmail account that I use for car shopping and other things that require an email address, but I don’t want to use my regular accounts - those car dealers just keep sending email after email. As mentioned, they are discontinuing the free accounts. Maybe I’ll look at the protonmail one.
Gmail is my strong recommendation. You won’t see spam and the reliability has been near-perfect.
I have used Yahoo for e-mail for over a decade. It has a precreated spam filter that gets most junk and you can make your own filters for the rest. It is generous with storage for free. Yeah they were hacked and it was crappy of them to not reveal it right away but between having two step authorization and changing my password periodically I don’t worry too much about that. Plus I would bet any service can and does get hacked.
You absolutely CAN be signed into two different email addresses with Gmail - I do so routinely.
I’d avoid Yahoo - too many people I know have had their accounts compromised.