If AGI is actually attainable, then, sure, planned economies will be more performant than market economies, especially for high value industrial captal equipment. No need for Gosplan to decide on your candy bars and craft breweries.
A market economy is a distributed compute engine. The main reason why planned economies do worse historically is because the amount of compute needed to actually account for everything centrally is so immense (and thus costly), the implementers necessarily have to adopt some kind of simplified model, and then you get divergence between what the plan says and what's actually happening.
It's not a given that this will remain true forever, although I don't think it's tied to AGI. One could argue that AGI push is the trigger for a massive increase in compute capacity and corresponding decrease in price that might make this kind of thing viable, but that's just wishful thinking, not a fact.
That sounds like the finance bro version of mystical woo. There's nothing special about it. There must be doctors who say diagnosis is an art form. But AI will still out perform the diagnosis.
AI can calculate stuff that can be measured and calculated.
But investing (in stocks or otherwise) is not that. Investing is about the phychology of the people (all other investors). If investors as a whole make stupid decisions, the market movements make their decisions correct (like the incredibly stupid drop in Nvidia's stock due to release of Deepseek). AI can be more objective and better at calculating facts, but it doesn't matter if the market is driven by emotions and people.