I have been doing serious riding for the past 55 years and I have always found that I needed to warm up by riding the first 10 minutes at a moderate pace. I need to give my body time to adjust and increase circulation, including that in my lungs.
You probably have some level of asthma and doubtful it is an edema, despite what you read on the internet. I was first diagnosed with asthma as an infant but I have never experienced stress induced asthma which is what you described. It took me decades to accidentally realize that when I traveled my sinus congestion went away and with no nasal drip there was no irritation of my lungs, particularly when sleeping. I realized that I was allergic to wheat and if I avoid any foods with wheat then no sinus congestion. Doctors were happy to proscribe corticosteriods which is a bit like using a machete to remove a splinter from a finger.
A bicycle requires 15% as much energy as walking but if you use too high a gear that benefit is negated. I like to have one "granny" gear that is low enough that I can go up anything, regardless of how steep or how far to get to the top. For me this is a 39/28 or 36 inches for my low gear. It is a little more than two rotations of the pedals for every tire rotation. Today there are rear derailleurs that will handle a 50 tooth cog and so having a low enough gear is not a problem.
Most doctors know nothing about nutrition and nothing about advising people engaged in physical activity. They know how to read the numbers for tests and so they treat the numbers and not the person. My life is too valuable to me to entrust it blindly to any doctor.