Welcome, and thanks for posting.
Earbuds for sleeping. I tried the Bedphones, after starting this topic:
They are without a doubt, the most comfortable for sleeping, but the sound and fit are not optimal. Sort of like covering a nickel with foam and attaching an earclip to it. And the wired version can be an issue if you toss and turn.
The KZ ZSN isn’t too bad (I put Spinfits on them). I find them more comfortable than most IEMs. I’m a headphone and not IEM guy generally. And the sound is OK. But it is a cheap IEM, and if it’s possible to be fatiguing in your sleep, it will be.
I think that there are sleep factors other than the earbud/IEM itself. Are you a side sleeper? What kind of pillow? I think that feather pillows are the most accommodating to something in your ear, followed by foam bits (like “My Pillow”) or something else that shapes well. Solid foam and memory foam not so much.
The Koss KDE 250 will fall off you ear if you sleep in them, but are in interesting choice for experimentation at $59 from Massdrop. NOT exactly earbud or IEM or anything else.
I’ve had them less than a week, but the Sennheiser IE 40 PRO may be one of the nicest all-around IEMs in the $100 range, and are not too bad to try and sleep in. However they do not have a MIC, so if you are awakened by a phone call, not a good choice. AND, the design is pro audio, so it is possible to pull out the connecting wires while you sleep. @Brause did a review of them, which got my attention. The single dynamic driver is very coherent, unlike multi-driver systems, and the driver they use is quite good indeed.
Someone else will have to address your comparison question.