The bag matters more than the logo on the barbecue.
Spend a small fortune on a handsome grill, then fill it with damp rubble masquerading as charcoal, and the afternoon will rapidly become an exercise in regret. There is a difference between fuel that burns predictably and a bag of mysterious black fragments held together by optimism.
There are two useful starting categories: lumpwood charcoal and manufactured briquettes. Neither makes you a better person. Both can make excellent food when they're produced properly and used for the right job.
Lumpwood.
Charred pieces of wood, often irregular in size. Good lump charcoal can light quickly, produce comparatively little ash and respond strongly to airflow. Large pieces can be useful in a ceramic kamado or for hot grilling, while tiny fragments can obstruct airflow and fall through the fire grate.
Quality varies dramatically: species, carbonisation, moisture, piece size and the number of stones and half-burnt scraps in the bag all matter. 'Restaurant grade' may suggest larger, harder pieces, but it isn't a universal manufacturing standard. Check the actual contents and reputable supplier details.
Briquettes.
Manufactured blocks of carbonised material, typically with binders and sometimes additional ingredients. Good purpose-made cooking briquettes tend to burn more consistently in shape and duration, which can make a kettle smoker easier to manage over hours. They may produce more ash. Inferior ones can smell unpleasant while lighting or break apart.
Don't assume every briquette contains dangerous chemicals or that every lump bag is naturally pure. Buy products specifically made for food cooking from reputable suppliers. Follow the manufacturer's lighting instructions and let unsuitable ignition smoke pass before adding food.
Other choices.
Coconut-shell briquettes are made from processed coconut husk or shell carbon and can offer dense, consistent fuel; quality still depends on manufacture. Binchotan-style white charcoal, associated with Japanese cooking, can burn steadily and at high heat with distinctive handling needs. It is often costly and slow to light, and not every grill is appropriate for it. Read the product instructions rather than assuming it behaves like supermarket briquettes.
Instant-light bags are convenient, but the added lighting treatment and starting fumes may not suit a careful long smoke. They're not my first choice when the aim is to manage a clean fire and taste the meat rather than the starter.
What the bag doesn't tell you.
A respectable piece of charcoal should be fully carbonised and dry enough to light consistently. If the bag contains fist-sized lumps at the top and a kilo of powder at the bottom, the charcoal isn't necessarily bad, but your airflow may soon be. Sort the worst fragments out before filling a kamado's grate.
Price per kilogram tells only half the story. How much useful heat does the fuel produce? How quickly does it burn? How much ash remains? A slightly dearer bag that behaves consistently may be cheaper in real cooking terms than an allegedly bargain sack that disappears while the chicken is still pale.
Which would I use?
For a kettle smoker and a measured low-and-slow burn, consistent briquettes are an excellent starting point. For a kamado, good large lumpwood is often what the manufacturer specifies. For a hot open grill, either can work; what matters is heat control and clean combustion.
Use a proper chimney starter or the lighting method appropriate to your cooker, suitable protective gear and an outside-only location. Never use charcoal indoors, in tents or enclosed shelters, even after visible flames have gone. It continues to produce dangerous carbon monoxide.
Fuel is not flavour wood.
Charcoal provides heat and a characteristic barbecue atmosphere, but if you want a distinct note of apple, cherry, hickory or oak, use a small amount of appropriate smoking wood in the right cooker. Too much wood just buries your dinner in smoke.
Buy one good bag, take notes about how it lights, burns and leaves ash, then buy it again if it works. You can spend an amazing amount of time arguing about charcoal on the internet. You could also cook something.