When period-proof underwear first came out, I admittedly thought the concept was gross — until I tried them. I've had way too many experiences of leaking through tampons, which always seems to coincide with wearing light-washed denim, and I am so thankful period underwear exists.
When I'm on my cycle, I wear the Thinx underwear to sleep, which is more efficient than having a few pairs of old underwear reserved for bleeding every month (and always leaking onto my bedding), and I love them. Thinx recently launched a sleep short with the same mission and concept of the underwear, and it sent me a pair to test out.
I personally think the Thinx collection of underwear is great for sleeping in and haven't had any issues with leakage, but if you're looking for something that just feels effortless, I recommend trying the Sleep Shorts ($50). Essentially, they're exactly what they sound like: sleep shorts with the period underwear built in. They're super cozy, and although I could feel more fabric than I would in a regular sleep bottom, sans the built-in underwear, they don't look or feel like you're wearing a diaper! As far as absorbency goes, the shorts are at the superabsorbency level and can hold four regular tampons' worth of blood, according to the Thinx site.
As someone with a fairly short and light cycle, these sleep shorts are great for me, and I will definitely be wearing them during all future cycles. They have my stamp of approval, but as with any period product, you have to decide what works best for you, taking into account comfort, safety, and what's right for your body.