Wait I think I know what you are asking...
I think you are saying that the smoke and fire particles are intermixed... That is, they occupy the same space. Some smoke particles are behind some fire particles, and some fire particles are in front of some smoke particles.
But you are seeing only smoke in front of fire, or fire in front of smoke regardless of where the particles are in space... The particles aren't drawing in the order you expeect them to be.
Making these two sets of particles different surfaces in the same mesh won't solve your problem. In fact it will make it worse because then even if the fire is really far behind the smoke it will still draw in front of it. At least with the fire being in a seperate entity, you get... eh I'll invent a new term... "macro-sorting" right.
"micro-sorting" the particles amongst themselves (another new term I just invented) is unfortunately, not possible in a single surface particle system. You can sort smoke particles with other smoke particles so long as they are part of the same mesh, but you can't intermix smoke and fire particles.
The particle system I used to sell avoided this issue entirely by just making each particle a seperate entity. The screenshots you have seen that mix particles, if they are from stuff made in Blitz, probably used a similar method. Unfortunately, one entity per particle means one surface per particle, and that comes at a much bigger speed penalty per particle than a single surface particle system. Of course it does allow you to use 3D particles which can look better than 2D particles in some cases.
I think you are saying that the smoke and fire particles are intermixed... That is, they occupy the same space. Some smoke particles are behind some fire particles, and some fire particles are in front of some smoke particles.
But you are seeing only smoke in front of fire, or fire in front of smoke regardless of where the particles are in space... The particles aren't drawing in the order you expeect them to be.
Making these two sets of particles different surfaces in the same mesh won't solve your problem. In fact it will make it worse because then even if the fire is really far behind the smoke it will still draw in front of it. At least with the fire being in a seperate entity, you get... eh I'll invent a new term... "macro-sorting" right.
"micro-sorting" the particles amongst themselves (another new term I just invented) is unfortunately, not possible in a single surface particle system. You can sort smoke particles with other smoke particles so long as they are part of the same mesh, but you can't intermix smoke and fire particles.
The particle system I used to sell avoided this issue entirely by just making each particle a seperate entity. The screenshots you have seen that mix particles, if they are from stuff made in Blitz, probably used a similar method. Unfortunately, one entity per particle means one surface per particle, and that comes at a much bigger speed penalty per particle than a single surface particle system. Of course it does allow you to use 3D particles which can look better than 2D particles in some cases.