You can either apply now ('outland') or when you are already in Canada ('inland'), which you could do by going to Canada tomorrow or later in future. Hard to say which may be faster. Inland - can get work permit while being processed, but work permit takes 4-6 months normally, who knows in covid times. If you apply now (outland) before you are in Canada, you will have to demonstrate your plans to return to Canada (job offer pretty good for those purposes).
Outland - no work permit while waiting for file to be finalized.
As US citizen, no visa required (visa waiver). Once in Canada, visit can be extended if file not complete after the six months usually allowed visitors.
Only wrinkle is that at border, can conceivably be refused if officer not convinced applicant will return, ie should not present as 'moving'. For US citizens, officers usually less strict on this point, but perhaps not a good idea to arrive at border with all worldly possessions. (Fine of course if you are moving and spouse 'helping you settle.')