yup the thing is they didnt say what items to buy haha, not local video
i asked shopee seller and recommended me to buy below , sorry for very crude paint drawing ahahaha

motor will be soldered then connect to pwm, then wall plug connect to dc jack and put black and red wire to the pwm

turn on power and good to go ? 

[attachmentid=11505872]

thank you both so much for the guidance

i feel that the original stock motor is 6mm in diameter? the one i bought from shopee has 6mm in diameter

from the below YT video is from minute 14:45 he started to show the stock motor head/connector from the original marble run set say the head is too loose xD

thank you for pointing out the motor used in the YT is from the shopee link which i see is 4mm, hmm cannot really test till i go back to my condo and get the marble set run xD

hopefully it fits else i will have to buy brass coupling shaft connector from 6mm to whichever mm the head size is 

manage to make it works, the pwm shows RED color indicator when power on, should be ok right, no need to have green light to be safe? xD

any keywords to search for or possible diy kind of thing to buy from shopee to house the pwm + motor + on off switch cos seems too bulky and messy to carry around without a "housing for them"

[attachmentid=11505905]

icic mostly u use for what purpose haha, thanks for the casing recommendation

i just realize the soldered red wire to the motor is quite flimsy

abit of pressure will tear off the wayar haha, or i can replace with thicker wiring ? hmm

or use black tape to tape off the wire so not so fast to break