Yes background checks are done when you get a DM letter. But the status might not get updated in the mycic account. In our case, my wife's mycic account was saying "we are reviewing your eligibility" and "we are doing background checks..." (probably not the exact wording, but that was the meaning) until she landed. Having AIP means you met eligibility criteria, having a DM letter means you passed background checks (and medical)...
Regarding the landing interview, yes both must be present. But there is no stress to have with this interview. It last 5-10 minutes maximum, they ask the PA: have you been charged or committed any crime in Canada or anywhere else in the world? Do you have any dependants that are not listed on that application? To the sponsor, they asked: you will have an undertaking engagement of 36 months starting today, do you still want to sponsor your spouse? Then they say congratulations you're now a permanent resident of Canada and they hand you the CoPR document.
