A musician in an orchestra and a solo performer in a folk club are in quite different situations. The orchestral musician is playing a long and complex piece of music, but is not trying to communicate with an audience in quite the same way. A concert soloist will nearly always play without music.

In a folk club, you have to be a performer as well as a musician. The music you are performing is usually a shorter and simpler, but you do have to communicate much more directly with the audience. Using music or lyric sheets is a barrier to this. It also makes it more difficult to develop the performing skills to deal with the times when things go wrong.

If you must use a prompt (and I understand that sometimes it might be needed) then it's best to have something discreet that the audience won't notice and that you can glance at without losing the flow or breaking the link with the audience.