They say not to start out with the C5 because it is more expensive. We have had one for over 12 years. A few months ago we bought a second C5 because we both needed to use it in the morning at the same time. We first started with an M1, but after three days we decided to order an A9 and C5. We always use the it with 4 of the 4x4 coils, usually stacked in pairs.
I fell over backwards 2 years ago from Covid weakness making my arthritic back worse than ever. I could not lean forward or bend without pain for hours. To fix it I would lay in bed and lay on the coils for 30 minutes. To wash dishes, load the dishwasher or vacuum I had to wear the C5 coils placed on my lower back, held in place by a velcro back support device. This took my pain away and kept it from coming back. The Anker Power Bank makes it portable to wear when working. I use trickle charge because some power banks do not recognize that there is a device using very low power and will auto turn off. We use the C5 when we take trips with lots of sitting. You can use it with the cars USB or a power pack.
My back issues started 18 years ago and have gradually gotten worse. I do not like using NSAID’s unless for short term issues. One thing you might look into is Sciatica. You described several issues that sound like what I experienced right before Christmas. I was sitting for 5 hours a day, which is more than normal. After 7 days I started to have a burning sensation in my right leg from the top of my thigh to my knee, also the right hip. I was worried it was hip arthritis because I had been having pain alternating between the two sides for days, just before the burning in my right thigh and right side hip pain severe pain started… It escalated quickly once it started, by the next morning I was bed ridden from the pain and needed a walker. The pain was excruciating. I spent the next 7 days in bed, using a walker. I tried putting the coils on my hip and leg but it did help. I could not think straight and felt like I was high on drugs from taking Advil and Tylenol. If I had been thinking straight I would have searched my symptoms right away, and not waited for 9 days. The answer was Sciatica, confirmed by my doc. Then I realized that left leg tingling and foot numbness off and on 5 years earlier was nerve compression from my arthritis, also intermittent hip pain for years. I saw my doctor that day, she confirmed my diagnosis and sent me home with 2 prescriptions, Meloxicam for inflammation and a mild muscle relaxer, normal strength ones, similar to Benadryl, keep me awake all night, my doc knows I do not react to drugs the way most people do. Meloxicam takes up to a week to work, I took it for 2 weeks. The muscle relaxer was a low dose and did not help much. I researched and joined the Sciatica Facebook Group. There are exercises on YouTube specific to the 3 different causes of the Sciatica. Decompression of the spine and, elevating your legs when you sit, and walking are good. Do not sit for long periods of time without getting up and walking. The PEMF needs to be applied to the lower back, no matter where the pain is!
I use my PEMF whenever I sit now. The more you use PEMF the better your back will be, whether your back is hurting or not, use it anyway. I cannot answer your question about sleeping with it. You may need to use the smaller M1 so there are no long cords to tangle. Preferably if you can, figure out a way to sleep with a C5.
I would recommend you start with the M1 and see if it works, then as an existing customer, if you decided to upgrade to the C5 later there is a substantial discount, only on the C5, not for coils or other devices.