you will mostly get taxed.
The logic is simple. You are bringing in stuff from overseas into m'sia. as a owner of a country, im sure you would like to know what comes in and out.
and if the item is for commercial purpose, meaning you want to sell it and get profit...guess what..i want a cut from this as well.

this is where tax & duty comes in...get it?

If the 20pcs of apparels are not for commercial purpose, meaning  you want to wear it..then you will need to explain that to the customs. They are like "diraja" in this part.

Anyway, you can always check if your items are taxable, as some items are relieved from being sales taxed/duty as well.
http://tariff.customs.gov.my/
cheers!