I feel for every parent with the SIDS risk, no-one wants to feel a child's death is their 'fault'. Yes, there are things you can do to reduce the risk, but for me, I just took a view that ALL I wanted to know was that my children were breathing properly.
You can't know that when you're asleep - even in the same room.
You can't know that from a video monitor.
You can't know that from a sound only monitor.
For me, the only answer was to get a monitor with a movement mat that would set an alarm off if they stopped breathing.
I went about my day during nap time, I slept soundly at night (haha, well at least when they were), I even (shock!) put them to sleep on their front when they had snotty noses because it could drain & they actually breathed better & got some sleep (and I did) when they were ill. But I knew that if there was a problem, I'd know about it in less than a minute - awake, asleep, or 3 rooms away. And that was FAR more reliable than checking on them every 5 minutes.
As they got older & occasionally shuffled into a far corner of the cot off the mat, there were some rare frantic moments when it bleeped away, but it gave me 4+ years of complete peace of mind across 2 kids.
Do what you need to get the balance right for your own peace of mind, but you can torture yourself trying to do the right thing constantly hovering, and baby could still stop breathing with you in the same room - so perhaps ease off on restricting what you can do while they nap & if you're concerned, maybe get a monitor that will actually tell you what you really want to know!