12V,20W bulb connection doubt
12V bulbs and the lamps in which you use them are in general NOT designed to be run directly off the mains voltage. They are designed to run with a transformer which provides mains isolation.

I would advise you to get not one but several transformers like 2 times 80 W or 4 transformers of 40 W.

Also 20W bulbs are very oldfashioned, why not get some LED lights instead, for the same amount of light you would only need one 30 W transformer.