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@SkinnyM Both topology layouts are generally acceptable for most hard surface models.

While the quad grid corner is a more conventional choice, the triangular quad corner tends to produce more appealing results for this type of shape transition. Something that can be verified by previewing the subdivision and looking at the mesh from multiple angles.

Comparing and validating different topology layouts also provides an opportunity to learn which loop routing strategies produce the desired results and when it makes sense to use them.

Although most flat surfaces are relatively tolerant of less than ideal topology layouts, as @sprunghunt mentioned, carrying some of these loops across the mesh does tend to produce more consistent smoothing behavior.

Which is why segment matching and controlling shape deformation, that's often caused by abrupt changes in the loop routing, is an important part of preventing smoothing artifacts on high quality surfaces and curved shapes.

So, although it isn't always essential for certain types of hard surface shapes, it is generally considered best practice to have relatively consistent loop paths. Even on flat surfaces.

It is possible to simplify the quad grid layout by reducing some of the edge loops into n-gons or triangles but since the triangular quad layout tends to be more efficient this type of topology strategy is often limited to specific edge cases.

Context is also important. Something that's passable in one situation may not make sense in another. Topology requirements for game art tends to be slightly more relaxed when compared to other fields like visualization, VFX, etc.

Recap: Test different topology layouts and compare the results. If the mesh subdivides cleanly and fits the technical requirements for the project then it's generally going to be passable. When it comes to hard surface subdivision modeling, focus on developing the proportions and shapes first then move on to work through the base topology flow before adding the support loops. This will make it much easier to solve loop flow issues and optimize the mesh.

Without HDR, and no material, but you can certainly add those if you like.

@Deqa The edges on the model look a bit too sharp when compared to what's shown in the reference images. Though the fender is mostly flat surfaces, there are a number of angled transitions that are missing. Some of which are difficult to see. Gathering some higher quality references, with better lighting and more contrast, would make it easier to see exactly what's going on with the shapes.

As far as the topology goes, though it possible to add all of the smaller scale support loops in a single operation, it will be much easier to do so once all of the larger shapes are fully blocked out. It's also completely acceptable to use support loops on just one side of a soft shape transition or to slide some of the double loops further apart to ease over the rounded edges. Just be sure to constrain any movement to the underlying surface. That way everything stays co-planar.

Looking at some additional reference photos: the fenders and trim line do appear to be single piece molded fiberglass. Something that should probably be added to the block out. Especially before generating the smaller scale support loops. Getting all of the shapes into the block out and figuring out the basic loop flow will make it a lot easier to decide which edges need support loops on one side and which edges need support loops on both sides.

Here's a quick example of what the rough block out could look like. Larger curves, like around the corners of the wheel well, can usually be added with single support loops. After all of the major shapes are present then the rest of the smaller support loops can be added with a bevel / chamfer operation.

Though there's a number of different ways to setup variable width loop generation, sometimes it's just easier to apply the modifier and slide the support loops away from the edges that need to be softened. Really just depends on what makes the most sense for that specific part of the model.

Soldeus Are there any specific areas that seem like they could be improved or concerns about the results? A bit more context on the intended use case would also make it easier to give actionable feedback.