Maybe I'm overthinking this, but I got two waterproof crib mattress protectors (to use with the crib) and two waterproof pads to use under the Pack N Play sheets. The waterproof protectors are rather thick/plush.

Per suggestions I've seen around, I just layered the crib mattress to have a waterproof cover, a sheet, another waterproof cover, another sheet, so if we have an accident during the night two layers can easily be peeled off.

I did the same for the PnP: waterproof protector, sheet, waterproof protector, sheet (we plan to use the PnP until she moves out of our room, and then switch to the crib).

All those layers make for a softer sleeping surface. Everything is pulled taut, but I'm not sure if this is a potential SIDs risk? Am I overthinking this, or should I err on the side of caution and remove some of the layers?

These are the mattress protectors, to give some idea: