Lines/no lines is a whole other debate. You will get people saying yes to both. When I started double bass I drew pencil lines at 3rd, 5th, 7th as reference points. As time went on those marks naturally wore off. By then my hand knew where to go (usually) and my ear guided on any correction needed.
There will always be dots at these points on the side of a fretless bg neck to give that reference. Eventually with practice your hand/eye/ear will coordinate and give you the right note. As always it will take practice.
Lines will give you more of a reference point. However, if you have a high action on the strings you are still going to have to compensate as when you press on the string you are stretching it. That will change the intonation point. If you have a very low action that's not so much of an issue.
If you start on an unlined board that cuts out one lair of learning, i.e. not having to learn to play without lines.