I understand that: in "asm" i have RedeemScript. In txinwitness i have my signature and the pubblic key. Correct?
Correct. in a P2SH-P2WPKH the witness contains the signature and the public key, and the script signature contains the redeem script.
is it correct to say that, as an additional condition, to unlock a UTXO P2SH-P2WPKH, compared to a P2PKH, ...
Because the address you are using is a P2SH-P2WPKH address as you mention (sh (wpkh ())), you get the output
It is talking only about the top level (P2SH), because it is a P2SH address, regardless of what the script "inside" it encodes. It doesn't "see" the underlying P2WPKH when you call validateaddress. The ...