I would like to know when creaming butter and sugar if it is better to use finer sugars, such as golden/white caster sugar, light brown sugar (I am in Hong Kong, and this looks similar to UK golden caster sugar to me) or icing sugar, in order to ensure that the sugar dissolves sufficiently? AIso I understand from previous ASKs that golden caster sugar and white caster sugar are interchangeable for cooking and baking.
Many sponge cake recipes, such as Nigella's Autumnal Birthday Cake, Lemon Polenta Cake and Red Velvet Cupcakes start by beating together butter and sugar, known as "creaming". This has two purposes; the first is to start dissolving the sugar and the second is to help incorporate air into the mixture. However you do not want the sugar to completely dissolve as the crystals help to cut into the butter to create air pockets, hence the butter and sugar mixture should be beaten until it is pale and looks slightly "fluffy", but not completely smooth.
For this you need a sugar with fine grains, but not powder. In the UK caster sugar (superfine sugar) is usually used as the crystals are smaller than those in granulated sugar. In other countries (such as the US and parts of Europe) white sugar is often finer than UK granulated sugar and can be used in most cakes and cookies. Soft light and dark brown sugars (and muscovado sugars) also have fine crystals and are good for creaming together with butter. Demerara, turbinado and some raw cane sugars (often sold for sweetening coffee) have larger crystals, are so are not suitable. We are not familiar with Hong Kong ingredients but from the description it sounds as if the light brown sugar there is suitable as a substitute for caster sugar. Generally we would not recommend using icing sugar (confectioners' sugar) for creaming with butter for cakes, as it is too fine and dissolves too quickly.