Q: How many bits of entropy is acceptable?

Linux: > 2000, historically encouraged applications to gather as much entropy as possible, even if it was unneeded and degrades performance.

*BSD: >= 256, Just enough to initialize the kernel CSPRNG.

Tor: was 128, onion v3 moved to 256.

Wi-Fi: 128-bit. WPA3 would support GCM mode with 256-bit.

Bluetooth: 8 bits.