I don't know what to do with my parents' placement

It's good to have many religious beliefs. No matter what religion you believe, don't be superstitious. Don't listen to teachers or mountains. Speak freely and avoid being cheated. Besides, as you said, there are only ancestral tablets at home. Of course, the ancestral tablet should be placed in the middle of the table (whether it is hung (nailed to the wall) or placed in the cupboard or on the table). Of course, the ancestral tablet is placed next to the tiger (facing the left hand side of the house). As for the statues (pictures or photos) of the three treasures, you can hang them at will. Personally, I don't think the pictures need to be presented, because they should be presented after the opening ceremony (I don't understand PS Buddhism). Also, the folding table can be used to worship the gods and ancestors (for economic reasons, I think it is enough to worship the gods and ancestors with heart). Otherwise, you can go if the board is big.