Not gonna lie, if I was powerful and immortal, I would force a dictatorship. It's not something I crave, lust for, or even think about regularly... but IF I had the powers handed to me, that is what I would do. The general population is far too stupid and unfocused to be making the correct decisions for humanity as a whole.
I would pick capitalism (or the hybrid mix of capitalism we see in developed western countries) over hardcore communism any day... but just because it's the best option we have right now, doesn't mean it's literally the abolute best option.
Honestly, I fucking hate the UN, and I think the world would overall be a much better place if war and conquest were allowed. This whole "countries are soverign and you can't declare war" is causing so much stagnation. A poor, developing country stays poor and underdeveloped because its resources are used inefficiently, whether due to lack of education/skills or corruption etc.
Whereas in the past, a more powerful, developed country would simply take over, utilize the resources more efficiently, and if there is any value in the native population, they would be left to enjoy the benefits of a more developed society/economy/technology... and if they were useless, they would be wiped out, and humanity would be better off for it.
The only problem I really see is slavery, which I'm not a big fan of.
But IMO survival of the fittest is essential, be it on an individual level, a species level, or a national level. The stronger, and more capable should take over the weaker and less capable, and integrate them in to society, and uplift them (by force if necessary), and eventually become one, stronger nation. That is far more conducive to progress than a thin veneer of forced peace over economic warfare, and stagnation, where the rich get richer, secure in knowing that no one has the right to contest them, and the poor get poorer due to being economically exploited by the rich, but never receiving any of the benefits of that exploitation because "you're your own soverign country, and don't deserve the benefits of our country, even though we secretly exploit your cheap labour and corrupt government".
Wars of conquest, and colonization wold be far better for everyone in the long run.