I had a similar thread here recently.
https://tfk.thefreekick.com/t/stoves-solid-fuel-gas-that-type-of-thing/33600/6
There’s a couple of terms you need to get up to speed on, like Balanced or Conventional Flue. So have a read about them. If it’s going in an existing fireplace then you’re probably talking Conventional.
I’d be more interested in the efficiency of the stove myself rather than the Kw rating. So have a good look at that.
Three types of controls. Manual, Slide, or Remote.
Then you have the fuel type. So you’re going to need to look at the regulations in your area. Not only what you can burn now, but the changes that are coming and what you can burn in the near future. Solid fuel is on the way out, rapid.
So once you make the above decisions you’ll find that the choice is limited. By that I mean it will be more or less made for you. Just pick a colour.
Found this brochure very informative.
https://brochures.stovax.com/brochures/pdf/gazco-logic-fires.pdf
Start with the technical stuff explained on page 44.