You will need to pick a case and then check what size mobo and psu it will accept.
Psu....you might want to shop for a modular unit as those small cases don't have much room for hiding the extra cables.
i want to build a simple build for web streaming downloading and surfing and movie watching no real gaming.. here is all the hardware i was thinking
mini itx mobo: https://www.amazon.ca/gp/product/B072BHBRTM/ref=ox_sc_act_title_1?smid=A3DWYIK6Y9EEQB&psc=1
power supply: https://www.amazon.ca/gp/product/B01MTZ96RU/ref=ox_sc_act_title_2?smid=A19N3NI8X4F24J&psc=1
ssd for operating system : https://www.amazon.ca/gp/product/B00OAJ412U/ref=ox_sc_act_title_8?smid=A1K2SUXU652HJB&psc=1
hdd for storage: firecude 1tb
now i want a mini itx cases because i want this pc to be as small as possible
should io be concern with the heat .. i do not have a graphics card so im guessing with a cpu fan it should be enough for the whole system
also all the links the prices are canadian i from there.. is everything compatible will everything fit in a mini itx cases