If you are approved then your province will transmit all your data ( whichever documents you submitted at the time you applied for PNP) electronically to CIC and cic will make sure if everything is in order or not and whether you meet the criteria. If everything is in order and you meet the criteria then the CIC will pass your eligibility
You can change jobs as long as you have open work permit but it is recommended that you stick to your current job until you get the PR. If you quit the job and cic calls to cross check with your current employer than you will be in big trouble. However the chances of cic calling your employer are very slim.