MC...
You are absolutely correct on both counts. Adding a cyclone actually reduces the efficiency (less "suction") of a dust collector. Adding a dust bag with a "finer weave" will help reduce the smaller dust particles in the air.
I'm sure I'm opening a can of worms but, what the hell...
Years ago, I worked for a major supplier of woodworking tools and equipment as an R&D machinist. One of the reasons I got that job is that I'm a life-long woodworker with sales experience... not only am I familiar with woodworking machinery... I personally own a lot of machinery and there are very few machines I haven't at least operated. My primary job was to work with our senior engineer... together, we would brainstorm new products. I would ultimately build working prototypes. Together, we would get products into production and into the market.
At one point, we decided to expand our line of dust collectors by adding a 3hp cyclone. We solicited samples from two different manufacturers, hoping to just "private label" an existing product. We tested the samples against our existing 3hp "4 bagger" dust collector. I no longer have the data but, there absolutely was no comparison. The performance of the 3hp cyclones sucked... and not in a good way. At the time, Oneida was the undisputed leader in cyclone dust collection. We bought one and began testing. Our goal was to beat Oneida at their own game. I'll spare you the blow by blow action but, after 2 years of testing and development, we built the best performing 3 hp cyclone on the market at that time. We didn't just beat Oneida, we smoked them. Having said that, our cyclone still didn't match the performance of our 3 hp 4 bagger. During the 2 years, my friend and I literally lived and breathed dust collection. I learned a LOT. When I left the company, my boss gave me the prototype that I hand-built. I still have it.
As far as filtering, I found a supplier while researching the subject. I know the "hot trend" now is using pleated filters. I won't say they don't work... they do... but they have their own set of problems. In our testing, we found that the most efficient filter media was a "shaker felt" that I obtained from "American Fabric Filter" in Florida. We used their filter bags,, not only on our cyclone, but on all the rest of our line-up. AFF will make custom bags... not terribly expensive... and their customer service is second to none. If your dust collector is a standard size, you could probably buy bags directly from the company I worked for... if they have them in stock. If not, AFF has made those bags for years... cranking a set out would not be a problem. For reference, OEM bags on most dust collectors are rated at 30 micron. The felt from AFF is rated at 5 micron... a definite improvement.
We could talk endlessly about sub-micron particles but... I'm not sure what that would accomplish. At one point, I did production woodwork in my own shop. I've had dust collection in my shop ever since I knew it was a "thing". I finally reached the point where I had dedicated lines running to each machine... and did my best to "seal up" each machine to capture as much dust as possible. What I finally realized is that its not realistic to think about collecting 100% of even saw dust, not to mention micro-fine particles. So... you do the best ya can and call it a day. I've been working with wood for well over 50 years. I can't even imagine how much saw dust I breathed in before I realized that was a bad idea. A couple years ago,, I had a ct scan of my chest... more recently, had a physical... not a single problem noted... everything is working just fine. I should mention that I've never smoked as much as a single cigarette... probably has some bearing on my health. When I was in sales, one of my elderly customers got into lathe turning... and he was pretty good at it. Apparently, he had smoked his entire life. Probably about a year and a half in, he developed breathing issues and was put on oxygen. Probably a year (or two?) after that... he was gone. No doubt, the dust got him. And, he knew it was getting him but he loved turning wood... refused to give it up. My point is, I realize dust can be a hazard but I don't know how a guy would totally eliminate the risk. As I mentioned, personally, I'll do the best I can to capture all I can... but, I'm not gonna give up working wood either.
Anyways, enough rambling from me... if there's any way I can help, let me know...
...D