I had two letters. First was the formal invitation that clearly stated the purpose of the TRV request i.e. to come to Canada before the PR to learn languages and basically starting the integration process. I did not mention the intention to get OWP.
Second letter, the letter of explanation, I described the minimal ties that there are, and what we will do in case the PR is denied. Basically showing that despite minimum ties, there is an option to go back and there is a place to live and things to do. I can't go into details as it's personal and just useless for you or anyone else. But you can get the idea.
I don't know if any of that this played a role in their decision.