If I delete my account will I still be able to send and receive emails through Thunderbird

You will need to always have an account, as Thunderbird is only an email agent, able to manage an existing account.

Thanks, but I meant a Mozilla account not an email account. I have read that a Mozilla account only affects Firefox syncing, etc and not your emails but don’t know whether this is true. Do you?

Mozilla is not an email account. An account with Mozilla is to log into whatever Mozilla website you access, but that is not an email account.