Our only concern is that if ever there is risk of any interview for physically collecting the cards, AND if my spouse’s explanation isn’t convincing to the immigration officer, then is it that we will be issued a departure order and in that case it might hamper my chances of sponsoring spouse again? Since spouse gets a departure order, she will have to run behind certificate of departure given by CBSA. I don’t know how that works and it will be too much of immigration stuff to deal with in addition to the already piling problems.
I doubt the certificate of departure issue will come up, really - although not so strong on the details of that process. Even if, it should likely not be fatal to a subsequent sponsorship again.
But I somewhat doubt it will come to that. One factor is that I /think/ they somewhat rarely issue a departure order to someone who shows up in Canada for the interview (it often is more of a test of whether the person shows up). You also have the option at any point in the process (at least before being found inadmissible) to renounce the PR status yourselves, and 'start over.' (One caveat - if one renounces while /in/ Canada, you'd have to manage the departure - I think they allow/provide for a conversion to a visitor status to give time for departure).
To reiterate: renouncing/having the PR status revoked isn't fatal to a sponsorship application. It might make it more difficult to get a TRV approved during the process, but mostly if the departure order process etc got messy (i.e. did not leave when told to).
So my concern will be is travelling to Canada before expiration of cards and put in a new application for renewal a better choice OR I’ll just wait for cards to expire and apply for a stricter process i.e PRTD. Even If they reject PRTD there will be no departure order because we wont be inside Canada anyways, so if need arises I can sponsor them afresh without any questions on departure order in the PR sponsorship application
If they accept PRTD means our status is safe and we are assured of PR cards. Is this correct assumption?
"Assured" is probably a bit overly strong, in that any time one applies for something new that requires evaluation of status they /can/ review entirely (and come to a different conclusion). And in terms of how long eg renewing PR card takes after a PRTD decision, it's not automatic.
That said: there seems to be a fairly strong culture of deference to a recent formal decision based on merits (eg the 'accompanying a citizen' or H&C decision), that is, not go through and overturn the previous decision
unless something significant has changed. By 'something significant' - hard to guess what might trip that, but an example
might be an obvious change in the marital/residency basis on which the decision was made - eg accompanying and it turns out the relationship had ended and the citizen-spouse went somewhere else so not accompanying back to Canada.
Small note: that deference to an IRCC decision for a PRTD seems quite strong for CBSA (i.e. they'll let someone with a recent PRTD in usually only with confirming questions), less clear for IRCC proper (for PR card renewal), although that may just be because non-standard PR card renewals are slow (we don't know if there's actually a lot of detailed review going on).