I never said Mao did not rely heavily on the USSR, so I will largely ignore those points as we do not really disagree.
Regarding the Mass Line, it is essentially the tactic of taking policy from the people, and having the party reinterpret it and enact it accordingly. It is a way to avoid commandism and tailism, and has been applied by various ML or Maoist parties. Maoists tend to believe it is universal, while MLs tend to believe it is particular to certain conditions similar to China's experience.
As for cracking down on excessive luxury, one example is the censorship of flaunting wealth on social media, and punishing those found guilty of corruption, taking bribes, etc. In China, the number of billionaires is decreasing, as the NEP-style economy is transitioning to a more advanced planned economy gradually.