If/once your application is approved and the card is issued, you may be required to pick it up at an IRCC office in person. This could also involve bringing with you any paperwork or evidence requested by IRCC to sustain your claims of residency in Canada in the applicable 5-year period prior to your application.
IRCC will not mail cards outside of Canada.
Should you need to go pick a new card up in person and your current card is expired, you will have to request a PRTD to be able to board a commercial carrier (plane, train, bus, boat) to travel to Canada.
I am not aware of any issue with mailing in your application from abroad, however, you can only be issued a PR Card in Canada. Perhaps others could weigh in on this part of your question.