Nested segwit (3-prefix addresses) can reduce the fee up to 26%
Native segwit (bc1- prefix addresses) can reduce the fee up to 42%
Just a small correction:
Using native segwit addresses, the transaction fee can be decreased even by more than 42%.
The transaction fee is decreased by 26% when there are 1 P2SH input and 2 output.
The transaction fee is decreased by 42% when there are 1 bech32 input and 1 outputs.
For example, size of a transaction including 10 native segwit inputs and 1 output would be about 722 vbytes and 1524 bytes. That's more than 52% reduce in transaction fee.
PS.
I used
bitmover's tool for calculations above.