What is the name of this drawing style?
Each artist is going to develop their own style. So, those images are examples of Ross Tran-style digital figure illustrations, notable for their vivid palettes and fantasy and sci-fi themes.  

In general, you're not necessarily going to be able classify every type of figure or portrait drawing into a "style" that is anything beyond the "semi-realistic" term that you found, or perhaps "slightly stylized". And unfortunately, neither of those terms hold much value. For instance, semi-realistic is a term coined by artists that simply means "I'm not trying for realism", which describes a great majority of art. It's sort of akin to referring to the Romanticism, Abstract, Pop art and all these other eras combined as the Semi-realism periods.

As it seems you're trying to analyze how to convert these images from digital to traditional media, it may help you to think of them in gray scale. Or, if you have access to digital tools or a black and white printer, to actually convert them to gray scale. That way you'll be looking at the stroke for their values and not getting confused by their "hues". Ross Tran's vibrant hues may remind you of cartoons, but I believe you'll think differently once you see the images in black-and-white.

Another point to make is that knowing the name of the style, in this case, doesn't really help in learning to draw it. What's going to help is finding examples of what you'd like to draw, and drawing them. And also just drawing everything else. While I can't speak to this artist's journey, many start by learning how to draw as realistically as possible, practicing and studying artistic anatomy and live models. As their expertise grows, they're able to bend the "rules" of anatomy and develop their own style.