It is for people who generate their transactions manually and would like them not to stick out in the blockchain.

Can somebody provide default options for various transactions on current versions of Bitcoin Core and Electrum?

Options to check are version, locktime, sequence (for every input, with or w/o RBF).

Let's start with most common ones.
legacy:
1) p2pkh > p2pkh
1) p2pkh > p2wpkh
1) p2pkh > p2sh/p2wsh

segwit:
1) p2wpkh > p2pkh
1) p2wpkh > p2wpkh
1) p2wpkh > p2sh/p2wsh