It would be really nice to enhance phonerlite with SIMPLE messaging capability with encryption capability

what does sips do when in peer to peer, does it use TLS for messaging ? 

if its not peer to peer, but through server, can it support end to end encryption (via OTR or some gpg keys) ?

Presently every message I receive there is a sound and pop up notification. There should definitely be a configuration option to disable each of these two independently. Kindly add this.

Yes, I got all the text messages. But when the other user is not registered, there is no indication that message didn't get delivered, but instead says OK (similar to when the other user got the  message). 

Even when phonerlite is minimized or message window is not active, there must be an option (separately) to no popup or give sound I think. Let us say someone is working (in the office) on something important doesn't want to be disturbed by frequent messages, and just wants to check later. And the pop up/sound is for every line you send. If you take a phone and text message for example you have option to turn these off.

yes doing in ini file works. 

Some programs don't put everything in GUI, they put in ini file. So this is a good solution.

But please put a comment in the ini file (in all your releases) saying tweak. Anything in ini that doesn't have GUI option can be commented this way. Would be useful for such new things in future too.