Every major country that has ever gone down the communist road ended up a dictatorship
While I don't think full-on Marxism is necessary and am in agreement on the democratic socialism, I think the reason for this is really more towards the political end of it than the economic.
If a country practicing a communist economy had a more representative/democratic political system from the start, I'd like to see how the results panned out. And I'd also like to see which came first, the dictatorship, or the communism. The former being first makes more sense than the latter.
Well I ask these cause authoritarianism seems counterintuitive to the main philosophy around Marxism. Saying "the proletariat should have greater value and power in a business, since they're doing the actual labor", but then rolling over and accepting a dictatorship where the populace has no political say seems nonsensical.
Hence why I suspect the authoritarianism must have come first. So I can't necessarily agree to "communism predisposing itself to authoritarianism" since it doesn't make sense for a True-Marxist society to want to accept that sort of government.
As for how to set up the government in a communist-economy state: probably more of a Republic. People elect multiple representatives, and these representatives meet and decide on policies for the country and how to run it