Sounds like an inept tuner to me if one can't tune a 2 stroke or a 4 stroke to idle, reading the foolishness and false information in those links. I'd avoid any posts from incompetent users that blame the engine. They likely also destroy their batteries as well unable to handle the electric component of the hobby also. The glow engine has been around 80 years, give or take? It wouldn't have passed down generations if everyone had the same conclusions of those not capable of learning but create misleading websites linked above.
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• what type of fuel or fuel mix

Most don't pay the hazmat fee and order online, or make home brew when they're a novice. Most 2 strokes you find left for sale today from distributors that have survived this long as going to provide you user friendly engines that work with the available fuel on the market. Any hobby shop where you pick up your fuel is going to only supply a limited number of choices these days, so it's simple. Generally speaking, 2 strokes often suggest 18% oil content. They will run on 0%, 5%, 10%, 15%, and 20% nitromethane content if not more. 10%-15% is the most common that you see today. 4 strokes require a little less oil content, and a little more nitromethane to perform at their peak. But are just as forgiving. I fly at sea level, so these statements are under these conditions. I remember flying in Santa Fe as a kid and with the high altitude, nothing ran right, so a lot of adjustments needed to be made. Power was compromised regardless.

• the ‘cool or the sound’ factor (after all this is the original cause of all ills)

You'll find sound to be a personal preference. I suggest you search the marketplace and other forums for a used engine, saving you a lot of money from Tower Hobbies current prices for engines and you don't have to break it in. Most like the 4 stroke sound over a 2 stroke sound especially in scale airplane applications. https://www.modelairplanenews.com/fe...sitor_pref_pop

• mess that it creates

I don't even worry about it. I bring my cleaner and towels, and it's just part of the program when I'm done flying and packing up. When I clean my toilet, trash cans, or come home from a day of fishing, I don't worry about the mess that creates either. That being said, fuel residue can be reduced if not eliminated. There is only a mess when the output of the exhaust isn't deflected away from the model you're flying. 4 strokes permit you to extend the deflector farther from the model without effecting performance or tuning, and I mean several inches. 2 strokes are far more sensitive to exhaust length and extension but a short deflector or side mounting of the engine helps considerably in reducing post flight clean up. I had an Ultra Sport with a OS 61 using a header/pipe for an exhaust and never had to clean the plane once. If you are asking about mess, this likely isn't for you. Glow/gas, you accept it as part of the activity.

• Maintenance

When you're done flying for the day, pour some ATF or Marvel Mystery oil down the carb on a 2 stroke engine to lubricate the bearings during storage or between weekend flying. 4 strokes have a nipple typically found under the case that you have to attach a fuel line to and inject the oil into that area to lubricate those bearings, often overlooked. Some add oil down the carb on a 4 stroke and it never gets to the bearings. Regardless of fuel you use, after run oil after a flying day is necessary to preserve the bearing life. One can upgrade their engine to ceramic bearings and avoid internal rust, but there are other components that can lock up over extended periods of time. I buy my bearings from Boca Bearings in FL. That's the only maintenance I've had to worry about. For extended storage, the fuel tank will have fuel residue that has to be cleaned out before you go flying again. After a couple of seasons, I'd replace the fuel lines. If you improperly tune your engine or select the wrong heat range, you'll cause glow plug failure, but otherwise I get many years of use out of them.

• original purchase cost is less of an issue but maintenance effort and cost is

Is this a statement or question? Let's take this space to talk about your glow fuel vs. gasoline comparison. It's not really correct to call it nitro. That term came from the car crowd, not the airplane crowd I believe? Glow fuel is a mixture of methanol, nitromethane, and oil. Nitromethane is only 10-15% content, and even the oil is typically 18% for 2 stroke engine fuel, and they are capable of running without nitromethane in the fuel, so what would you call it then? It produces more power than the gasoline counterpart, displacement for displacement. So the gas engine is going to be heavier, turn fewer RPM, and is a rather new technology they've been working on to improve tuning to match that of the glow fuel engines. Some companies do it better than others. These are also expensive engines up front, and pay you back in fuel savings over time. But I'm not a fan of storing gas, mixing my own fuel, paying the up front cost to see if I got a good engine or not, don't want the additional weight, and I still get glow fuel for $12/gallon in Orlando FL (Graves RC) which isn't that much of a drive for me. I'm familiar with glow engines (45 years) and have dozens of them laying around waiting to go on an airplane. No reason to buy anything else. That's just my circumstances and taste. More power to the modeler that abandons the glow and goes gas. It's not irritating to me to wipe down a plane with 409 cleaner and some paper towels if necessary, and to others, they hate it. I guess the fact that I've changed my sons diapers, clean my own house, do my own laundry, all things considered, I find castor residue far less offensive to me?

• and which brand is better

Again very subjective and no right answer here. If this were a car topic, is Ford, Dodge, Chevy, or Toyota better? If you're pulling 10,000 lb trailers, which is better then? Some like Saito for its characteristics, some like OS, and there are others. Today, not many glow powered engines have survived the decline of their popularity as electric dominated the hobby. What's left is "better" than what failed and left the marketplace. Most like OS 2 strokes for the tuning ease and they forgive poor tuners. Unfortunately the nickel liner process vs. a true ABC engine, they don't take abuse well or last nearly as long, meaning 5 years vs. decades. 4 strokes you don't have to worry. All manufacturers make a long lasting 4 stroke if properly maintained and you use a tach, tune it in the proper RPM range, prop (load) it correctly, etc.
If you decide to get into gas or glow, I watch others who pay a premium for gas and do just fine, but I've yet to see one perform as well as glow or be as lightweight. For the amount of flying you do a month, would determine if the fuel savings is right for you to make gas truly worthwhile an investment, and go through the learning curve on brands, tuning, etc. which you would do anyway with glow to some degree. But, I suggest you shop from FB, CL, local club, or RCG, find a local sale with the engine, servos, and plane ready to go as a used package that someone no longer wants, than piece meal each or buy new. Doing that, you'll always find glow and very few gas powered plane packages, but you'll get in the air on a budget, especially if this is just an experiment that you may not continue, at least you got in the air for a lot less money and can always get out of it for what you paid.