What are the chances of accidentally sending satoshis to an incorrect (but in use) BTC address, if a single character is mistyped in a Bech32 (SegWit) address?
The chance is very small if it is Bech32 address. You will see the address not valid in nearly all cases.
bitcoin address are a pubkeyHash encoded in base58 with something called a checksum and version value
This is more about legacy addresses and not segwit. Base58 addresses are the P2PKH and P2SH. OP is asking about Bech32 and not Base58, but you are right about the explanation. Bech32 is more advanced in checksum than base58, which means the chance of sending to wrong addresses because of typo is significantly lower in
Beck32Bech32 than in base58 addresses.
Edit:
Why not just copy and paste the address instead? You can check and recheck the address characters in case you want to avoid clipboard malware or just use QR code which is resistant to clipboard malware. Also avoid malware generally.