Hi WrinklyMedic. Welcome to the forum. That is a good video showing off the two smokers - thanks for sharing .
A few observations that may help...
The cold smoker looks just the job and it is good to see that the snake in the smoke generator is going transverse as this helps to make the burn more reliable.
Do you find that you need to use the ice bags to cool the smoke? I would have thought that a simple fan keeping the air moving underneath would do the job. If cooling the smoke is a problem then you may want to replace the reflective metallic duct with a thinner one to allow more heat loss. Maybe I read the video wrong and the ice bags were to cool the chamber. If the ambient temperature outside is too hot to smoke then the ice would probably be more efficient if you put it inside the smoking chamber while you are smoking. With the smoker in the shade I find that it is only during the hottest summer days that it really gets too hot. When that happens I just smoke overnight when it is cooler.
On the hot smoker you may want to change your thermometers. I am not sure what the thermometer at the bottom of the unit is doing - it is way too close to the coals to be of much use and the "Warm - Ideal - Hot" on the top one does not let you know what the temperature is. You may want to invest about £50 on a dual probe digital thermometer (like a Maverick ET-732 or 733) that you can clip onto the cooking grate.
You will probably not need the additional screen. There is a reasonably gap between the two units and heat rises and will quickly dissipate. Even if you do get a slight warming effect into the cold smoker, how often are you likely to be using them both at the same time?
One thing I would seriously urge you to consider is to replace the hot smoker completely. A quote from another smoking forum... "Meco is a badly designed water smoker, with some mods it maybe useable but that smoker has caused a lot of folks to give up trying to cook Q."
If you want to try to do any serious low and slow smoking then the lack of air control on the Meco smoker makes temperature control very difficult without serious modifications. If you intend keeping it take a look at the ECB threads on here for the kinds of modifications that you can make to help. Alternatively you could invest in a Weber WSM or one of the ProQ smoker ranges to take its place.
Things like sausages and chicken you will probably find will be fine in this but trying to cook brisket, pulled pork or even ribs is likely to be more hit and miss.
The cold smoked fish looks good. As you dry brined (cured) it before you smoked you do not need to keep it chilled in the smoker. The three main ways that curing and smoking preserves the fish are 1-Increase the salt levels, 2-reduce the free water content, 3-the smoke acts as a mild antibacterial. Smoking for 24 hours at a temperature of around 25 C will help remove the water faster and will actually do more to preserve the fish. To do this though you do first need to start removing the water with the cure. Things like shellfish though do need to be kept cool when being smoked.
Cheese will be great in your cold smoker. Don't forget that the cheese will improve over several weeks after it has has been smoked. It takes 2-3 weeks for the harsh smoke flavours to mellow.
It is not a good idea to cold smoke shop bought sausages. You were right to hot smoke them.
I am looking forward to seeing more of what you are smoking. Please keep posting photos.