Dressed salad goes limp within a few hours. The components keep separately for 3 days and the chicken is good cold. Keep feta in its brine.
A traditional horiatiki has tomato, cucumber, onion, pepper, olives and a slab of feta — no lettuce and no chicken. This is a fair adaptation, but worth knowing the difference.
Yes, if the dressing stays separate. Chop everything into one container and dress just before eating.
A grill or grill pan gives the best flavour, but a hot skillet works. The key is not moving it for the first 5 minutes so it develops a crust.