Originally, a “tankie” was a Stalin apologist, but in more modern times, it’s come to mean just authoritarian communist. I don’t think it’s a self-applied term. More a derisive term used by anti-authoritarian leftists.

The anti-authoritarian communists tend to call themsleves anarchists, anarcho-communists, anarcho-syndicalists, left libertarians, etc. And they’d strongly tend not to have anything good to say about Stalin, Mao, or the CCP.

(There are right-wingers who call themselves “anarchists” or “anarcho-capitalists” or “voluntarists” or “minarchists” or “Libertarians” (note the capital “L”) or whatever, but they have pretty much nothing to do with the hard-left-wing anarchist movement that they appropriated the terms “anarchist” and “libertarian” from.)

Stalin and Mao were good actually, the CCP has never done a bad thing ever, and Russia should roll over Europe with their invincible tanks, because the west is bad, therefore anyone who disagrees with the west is flawless.

That may be an uncharitable exaggeration, but surprisingly not by very much.