Well, I don’t know what details you’re looking for. But here’s as far as I know/understand:
DPI on encrypted traffic is extremely difficult (impossible today as far as I know) to perform even by nation states. This will especially be true for Mullvad, Proton, and IVPN because they are well made, audited, well maintained, and stupendously run by experts using open source tech.
Read here about DAITA:
This feature makes it even more difficult or almost impossible (for all intents and purposes) for any entity to analyze your internet traffic, even encrypted.
Furthermore on why it’s difficult:
Strong Encryption: Modern VPNs use robust encryption ciphers like AES-256, which are computationally infeasible to break with current technology for general-purpose decryption. Think of it as trying to pick a lock with billions of possible combinations. Brute-force attacks would take an astronomical amount of time and computing power.
Perfect Forward Secrecy (PFS): Many VPNs use PFS, which means that even if an encryption key is compromised, it cannot be used to decrypt past sessions. This significantly limits the impact of any potential key compromise.
Short Key Lifespan: Regularly changed session keys limit the time window any given session is open to attack.
In other words, nothing to worry about for now and the near future if you are using the right tool implemented in the right way on your well secured computer preferably running macOS or Linux (mainstream distros with mainstream DEs - Fedora, Pop, Mint are all great options).