South Indian jewellery names pieces by where they sit. A necklace — attigai or short necklace — sits at the base of the throat. A haram is long, falling to the mid-chest or stomach. They are not alternatives so much as different registers, and at a wedding both are worn at once.
A short necklace sits close to the neck and frames the collarbone. A haram is substantially longer and hangs in a visible curve, usually with a large central pendant — a dollar, a kasu mala of coin units, or mango (manga) motifs repeated along the length. The longer drop is what makes a haram read as formal: it needs a neckline and a posture to sit against.
Because a haram covers more length, it carries more metal and more weight, which is why gold harams are usually reserved for occasions. This is the clearest case for imitation: a plated haram gives the same visual mass at a fraction of the weight and cost, so it can actually be worn for a full day of functions.
Daily and office wear: a short necklace or a mugappu chain. Festivals, temple visits and family functions: a short necklace, optionally with a haram. Weddings and receptions, especially for the bride: both, layered — the short necklace at the throat and the haram below it, so the two fill the space between neckline and waist.
The rule of thumb is contrast in scale, not in style. Keep the two pieces in the same finish and stone family — antique gold with antique gold, AD with AD — and let the difference come from length. Matching a heavy haram to an equally heavy short necklace crowds the neckline; a slimmer necklace above a broad haram reads better.
A haram is long enough to fall to the mid-chest or stomach, well below a short necklace. Exact lengths vary by design, and layered bridal harams are longer still.
Yes, and it is a common way to wear one for a festival or a temple visit. Layering the two is mainly a bridal and reception convention.
A kasu mala is a haram built from repeated coin (kasu) units, traditionally stamped with a deity motif. It is one of the oldest and most recognisable South Indian haram forms.