My dc have a standard bread/wrap with protein in it (meat/cheese/hummus), a tub of 'crunch' (tomato/pepper/cucumber/celery/grapes etc), a 'pudding' (muesli bar/fruit bar/flapjack/homemade equivalent) and a bottle of water.
Alternatively they get last night's leftovers. Ie something that is nice cold, like chicken drumstick, fish finger sandwich, or jacket potato and beans or tuna mayo. They don't like pasta salad, but that would be an option if they did.
I'll often batch cook drumsticks and freeze them in bags of 3 (3 dc).
Peas and sweetcorn are a good addition to the salad tub, and don't need defrosting or cooking.
If they ever have anything which needs a spoon, then the item and the spoon to into a sandwich bag inside the lunch bag, with strict instructions to be returned in the sandwich bag to avoid smeary mess in the lunch bag itself,
I only made packed lunches because I had to. From about Y4 or 5 my dc know that, if they want a packed lunch, they have to make it themselves. I will help if asked appropriately.