Can I skip meringue from a recipe? Because almost all of the recipe, even tiramisu, has meringue in it.

I may be wrong, but I think the recipes in your book refer to the meringue technique, rather than the actual standalone meringue sweet. In both cases egg whites are whipped with sugar, but in the case of the cakes, those egg whites are then added to the cake batter before baking, not cooked on their own. And recipes for chiffon cakes have a lot less sugar than recipes for the meringue sweet, especially if those recipes are from an Asian source.
I would not recommend cutting down the sugar unless you have experience with these cakes. If you want to know whether your recipes are on the sweet side or the mild side, I suggest comparing them to some of the recipes on the kitchentigress blog. I have tried many of them and they work perfectly while being very mild on the sweetness. And to give you a direct answer, no you cannot skip the meringue technique in a cake that calls for it because the structure of the cake depends on it.

You might be able to reduce the sugar slightly (i'd say by no more than 1/4), but you will still need the beaten egg whites for lift and dryness. Sugar does more than add sweetness. It also contributes to browning, and is a significant component of the alchemy that is baking. There are cookbooks that are devoted to low sugar baking (both Joanne Chang and Cooks Illustrated have recently published them.), so it might be better to use recipes that are designed to be low sugar that have been tested and are known to be successful.

I'm not sure what you're asking. Can you tell us what recipe you're working with? Whipped egg whites (meringue) are generally used to lighten up the dish using the air that you beat into the egg whites. Without them, tiramisu, for example, would be dense like cheesecake. I hope this helps.