I would say that Chronic Lyme is unlikely Classic Lyme disease caused by a tick but a novel (likely autoimmune) condition that might be found to be ''ME'' in the next few years. Inside that, a significant proportion of CFS will become that new illness.
Then we get more complicated, potentially:
This 'new' version of Lyme (e.g.autoimmune) might only apply to one subset of ME/CFS/Chronic Lyme. For example, we know that (from ME CFS research) that Slow Onset and Sudden Onset ME CFS seems to have different outcomes implying they are either subsets of the same condition, or not related at all. We simply don't know. So take that on board.
From what I can see anecdotally, there is something making people with a whole host of conditions, test positive with a Cytokine reaction for Intracellular Lyme. This is of course equally fascinating, as it is worrying. It's hard to know why, but we might have some answers when better tests are developed, such as DNA sequencing tests that can pick up not one strain, but maybe 10-20+ from a single drop of blood. The two tier Lyme test, is inadequate, we all know this and will miss many people because there are 100 strains or so of Lyme, and only a handful (5 or so) that can be tested for commercially!
What we do know is CFS can never be Lyme or ME because of how CFS is diagnosed. With CFS, all you need is self reported Chronic Fatigue and 4 or more symptoms and in the UK, just 1 additional symptom and self reported PEM. Due to this very weak criteria based on symptoms not signs observed by a doctor (subjective not objective analysis), people with ME or CFS diagnosis will inevitably find out they have many different reasons for feeling ''fatigue'' and don't share the disease or syndromes they believe they did, with others with the same illness label.
To get back to your question:
One of these conditions may be the original Lyme disease caused by the Borrelia Burgdorferi tick, and another may be the newer form that researchers haven't published on yet that appears to be associated to ''ME', or what people refer to ''Chronic Lyme'', e.g. the likely autoimmune illness, aka Post Treatment Lyme Disease Syndrome, aka, the 'persister' group, aka Late state Lyme. (All these groups have been thrown in together, subsets of Lyme, that are different to classical Lyme as these patients don't get better with short courses of antibiotics).
So in conclusion if someone believes they have Lyme, first of all they need to have signs of it, and ideally a test, or a diagnosis from a doctor. Having said that, the CDC say Lyme is a clinical diagnosis and you don't require a test, but it's helpful of course to have irrefutable proof. Thus Lyme can be diagnosed in the same manner as ME CFS - I wonder what phenomena that might lead to if Lyme and ME CFS have very similar symptoms?!
As for figures of how many people have 'it', first we need to establish what 'it' is. We can guess this will be a subset, and that subset may well me 90%, we simply don't know. However, anyone can say anything on the internet and as Valintijn says in the posts above mine, what people say online needs to be taken with a pinch of salt, because some have little knowledge about medicine and science and tend to get sucked into a 'herd' response on Facebook Twitter by others. This isn't to belittle them or disrespect other patients, it's just a human phenomena of influence, worsened by people feeling desperate and wanting answers as they want to feel better, and the official response is usually you're either making it up, or we don't know why you're sick, goodbye.
Hence the patients are left out in the cold, with no where to turn. And also 'the patients' doesn't mean they are the same patients as you or I. We will likely all end up in different subgroups with ME CFS, as the science progresses and that will apply to 'Chronic Lyme' patients also.