You haven't been an ex smoker for that long. When you quit smoking, the small hairs (cilia) on the inside of your lungs start to grow back and it starts to break up all the crap that is coating the inside of your lungs. When smoking, you burn away the cilia. Anyway, as that stuff breaks up, it can cause the wheezing you experience. You notice it more when laying down because you are more at rest and more in tune to what is going on with your body. Also, it is probably much quieter and you hear it better.
Very good point ^^. OP, how long have you been off the cigs? I have quit in the far past, cold turkey (lasted about 3 months). Even with complete cessation of any nicotine consumption, I had many physical symptoms as the effects of smoking left my system. The heavy chest when laying down never quite went away then (well, too short of an experiment, since I went back to smoking). Wheezing, smoker's cough dissipated some after 1 month.
This time, quitting with vaping, the physical expunging of the smoking tar and junk from my lungs took a similar time frame, maybe a little shorter, since I cut way back for a month or two before going 100% vape. I'd say maybe the vape, but seriously consider the effects that smoking cessation can cause. Somewhere there's a long list of symptoms of quitting smoking, not just quitting from vape, but any smoking cessation protocol, people can experience similar physical effects.