Which are your favourite privacy coins?
&
Which essential features of a privacy based currency have your picks implemented?

is the Best and reason is its Handled from telegram and its not only privacy coin but it is messenger based. BITSUM use
CRYPTONIGHT Algo.
BITSUM Have High Degree of Confidentiality in Transactions.All your Transaction will Be Private and Secure, Send BITSUM Anywhere in the World.
How exactly are you supposed to retain privacy when using a messenger that is linked to mobile phone numbers...?
Its privacy,
Mobile number is only used to create an account but no one can find your wallet address using that mobile number.
if you think that it is linked with mobile number and can be traced then all wallet installed in a system can also be traced using IP address.
mobile number has nothing to do with that