There are mini-fridge sized curing chambers for home use. You can buy cellulose aging wraps, which is what I'm using at first, and nowadays there are permeable vac bags designed for dry aging as well. Haven't heard much good about those though, very difficult to establish and maintain a proper seal. The sheet wraps came recommended. I don't know enough about ideal temperatures and humidity just yet, I'm only beginning this foray myself, but a stable environment, cool, low humidity and decent airflow makes sense to me. Humidity being the most important factor. Then, as long as you use the correct type and amount of cure salt it should be a matter of patience. Like a less than ideal environment will still work but may take a bit longer.

Fresh sausage from a supermarket meat counter (where I live) is probably fairly close to what I make. However they'll probably use some fillers and excess water to save money. The pre-cooked or frozen stuff you'd buy away from the meat counter is more likely to be loaded with additives. As for sawdust, well that's a butchery term for the emulsion of meat, fat and bone that collects in our bandsaw. It's not wood mill sawdust, we just call it that. If it's collected while still fresh there is nothing nutritionally bad about it. I use it in dog treats all the time. I WOULD NEVER FEED IT TO A HUMAN as I pride myself on producing too quality fare but it's not the end of the world some cultures add it to their sausage farce (looking at you Australia). As long as they're open and honest it's going in there, and using it safely, I see no issue. My shop generates less than one pound of it per day at peak so it's not exactly going to make us millionaires.

My only gripe with grocery store sausage is they're all the same tired and played out recipes. I pride myself on producing recipes and versions of products nobody else is making. You want a Hawaiian Pizza Sausage? You have to buy it from us. My Chipolatas recipes brings the sausage full circle back to its ancient Roman roots via the caramelized onions. I chose to do that when nobody else was. It elevates mine above the generic, corporate approved safe bet.

I have never sous vided a steak in my life. Nothing against it just not my style. I'm a cast iron pan sear guy. Love the crust texture.

As for sausages yes you can absolutely sous vide. You'll want to use cure salt as the cook will hold the meat in the danger zone for some time. Using cure salt and sodium erythorbate will give your par cooked sausages a long shelf life in the fridge. Many people hosting or catering cookouts will par cook sausages in advance like this so they can be quickly seared and served at the event. Quite popular preparation. After sous vide give them a couple minutes ice bath then rest at room temp for 30 minutes before packing and refrigerating.