It does mention in first light novel that when changing clothing as in equiping new stuff there's a couple seconds lag where your avatar is in its underwear before the new equipment appears on (if doing a full clothes change though not just adding something on) and it mentions that girls would go get changed in privacy whereas guys were fine standing in underwear for a couple seconds (go figure..)

But like i think with armour changing you do need to unequip old then equip new but its pretty much just button pressing for like equipping i think so pretty quick and simple