The modeling in a lot of these assets is often a matter of simple cubic and cylindrical shapes together; as such they almost always begin with a cube or a cylinder. This is very conventional 'box modeling' with no real tricks. If you have strict triangle requirements you must be considering which details really need triangles and which the texture can handle during the whole modeling process. These models don't look very interesting at all without textures; they are chunky and basic - they likely would not impress many people. The textures are what makes it worth looking at, and the UVs are what determine how much of our texture is really used on the model. UVing is perhaps the stage I see most-neglected by beginners; and even by more experienced artists.

If I recall correctly, only the castle and one of the larger houses in this image used anything larger than 256x256 - you can extract much more texture area from maps than might initially seem possible if you take great care to create UV layouts with minimal unused texture area. This includes stacking UVs to re-use part of the texture on multiple parts of the model (this effectively means you are increasing texel density without increasing texture size). But if your engine uses a decal system overlapping UVs might not be a good thing; you must know how your model will be used in-engine.

Any modern game engine should also be able to handle floating geometry, too; some people don't seem to realize that it is okay to have polygons that are not attached to the main polygonal structure, 'floating' in place - as long as they are 'merged'/'attached' so that the computer treats them as a single object. This can be a valuable way to reduce object complexity compared to trying to merge all vertices, but might also waste texture area depending on the model; it is up for you to decide which trade-offs are worth it, which will likely also be dependent on the strengths/weaknesses of whatever engine you are using. Floating geometry will also break triangle strips, but that is a topic that is likely more technical to discuss than is worth it.

I suppose my main point in this is that there are very few tricks used in these assets - the modeling especially is *very* simple and usually requires only the most basic modeling methods to accomplish. Creating appealing assets doesn't require complex processes, it just requires a deep understanding of how to best utilize your toolbox of processes so that you can pick the right ones for what the model needs to accomplish in-game. Whatever style you are modeling in will usually not be especially relevant to the processes you end up using - as long as you have strong modeling fundamentals you should have little problem analyzing concepts and coming up with good geometric solutions regardless of if they are cartoony, realistic, or somewhere in-between. Based on your gallery it looks like you already know the tools needed to create these kinds of assets; basic extrusion, vertex/edge movement, collapsing, and the other very common related functions - these few things are 90% of what you will use. Just work on practicing with them a lot, and experiment with new techniques/methods whenever you get the chance. You may discover something that you will recall in the future to put to use.