I don’t think this fits the technology: blockchains are perfect for totalitarian states since they prevent anyone from hiding from the tax collectors and police. The only way it helps is if the government is too weak to enforce its laws, at which point that’s probably the least of your concerns.
Only if you use chains with traceable transactions.
The schemes Zcash and Monero use have never been tested at scale with a sophisticated adversary. The statistical methods used are probably fine for keeping your friends from knowing what you buy but it’s less clear that a government which can observe network traffic and receive KYC data from compliant merchants or compromised devices won’t be able to rule out some of the decoys over time, and since it’s a blockchain you’re gambling that this will hold true forever.
Monero's ring signatures are not the same as ZCash's zero-knowledge crypto. Monero obfuscates, but ZCash hides completely, cryptographically.
https://crypto.stanford.edu/timings/
Nation states are some of hardest attackers since they can do things like monitoring network traffic to correlate with chain activity or compel some fraction of the participants to surrender data. I know some smart people work on Zcash but there’s no safety net when all of the transactions are public and immutable.