TRV is more dependent on how strong your ties are to your home country and your purpose of travel.
If an invitation letter is given by a friend then you have no way to prove your relationship with them, the only thing that will support your application is financial strength, your own travel history, and your ties to your home country. The host can mention in their invitation letter how well they know you (e.g. number of years, how you met them) etc.
Good luck!