Since you’ve already done a medical for your PGWP, IRCC may simply reuse yours from their system (provided it’s still valid). For your common-law partner, it’s generally better to wait until IRCC sends the medical request (IME) with the appropriate form and UCI number — that way you’re sure everything is linked correctly to your file. But you can do upfront medical exam also and update them .
For your change of address, since you don’t have an AOR yet, you won’t be able to link the application to your IRCC online account or use the change-of-address portal.
Until then, the Webform is the correct route — just choose the option “I want to report a change in my address” and include your application details (full name, DOB, date and type of application, UCI if you have one, etc.).
Once you receive your AOR, you’ll be able to link the application to your IRCC account and update any future changes there more easily.