In English I would say, I'm getting dressed right now. I'm cooking dinner now. We wouldn't say: I get dressed now.. I cook now...
I notice in Spanish you can say: Me pongo la ropa ahorita. Yo cocino ahora. When do you say: me estoy poniendo la ropa or estoy cocinando? Do Spanish speakers prefer the simple present when describing an action in progress OR Is it a regional difference that differs from country to country?
Its a personal preference, the meaning is the same. There is no difference between "Estoy cocinando", "Estoy cocinando ahora" , "Estoy cocinando ahora mismo", "Cocino ahora mismo".
Its better to handle in simple present, here you have some corrections:
I'm getting dressed right now => Me estoy vistiendo (o poniendo la ropa) ahora mismo.
I'm cooking dinner now => Estoy cocinando la cena ahora mismo.