Is it possible for me to SSH to my server like this [...] it simply logs in, without a password and without an ssh-key.
Yes, it's possible with OpenSSH at least, by disabling the requirement that passwords be non-empty in the server's sshd_config file.
It should also work with SCP
SCP does not have its own authentication, it literally just calls
ssh for the remote connection.
my remote server's firewall is configured to allow only my specific home IP to connect to port 22 and because of this I am not worried about security for this test.
That's not a very good excuse – IP address is one of the weakest forms of authentication there is. For one, the server doesn't know whether the connection is made by your actual PC, or by an infected device on your home network, or by your guest/neighbour who is on your home Wi-Fi.
Linux firewalls are also more likely to fail open: if there's a syntax error in the ruleset, for example, it might revert back to allowing everything from everywhere on reboot. (Whereas if you make a mistake in authorized_keys it still doesn't allow anyone except valid key entries.)
And maybe I also plan on using a very complex username such as "user_name_82391274829"
You just invented a password.