Greetings!
I’d be very leery of those brick ones inside, and the cost of candles can add up big time.
I have seen some conversions that have replaced was candles with oil filled ones with wicks. These are very versatile, multi fuel, cheap, and pretty safe to use. One of these conversions on Youtube converts a UCO Candelier 3 candle job to a 4x oil candle one. The original one is rated at 5k BTU, the conversion would likely up that by at least a third. Here’s a video about the conversion:
I have a Bunsen Sports Heater / Cooker that I use and love:
A friend has an Origo Heat Pal, but uses either kerosene or vegetable oil in it instead of alcohol. Like the Bunsen, it’s both a heater and a cooker.
https://www.google.com/search?tbm=vid&q=heat+pal&oq=heat+pal
I also have a big 23k BTU kerosene heater for extreme cold weather use, which can also be cooked on, but it is overkill for most people.
Many people also use a pot of sand or dirt on top of their camp stove.
Cheers!