If I obtain a young professional work permit, can I change employers during my stay?
No. This will be a “closed work permits”  or “employer specific work permit”, meaning that you may only work for the employer whom you have applied to work for during your work permit application process.
Should your situation change during your stay, you will not be able to take on work for a new employer without requesting changes to your work permit conditions, which may be approved in specific circumstances, but are not guaranteed and it is a lengthy process.