c ++ – 2D isometric pixel art technique

I recently started working on a project that is to develop a game similar to the original for Gameboy Advance (the handheld version of the game developed by Griptonite Games). This is mainly a project to learn how to create a video game from scratch, especially in 2D (isometric in this case). I plan to use C ++ with SFML for this project. I already have some programming skills, but as I also like to draw the art myself and have no experience in it, I wondered how I could do it.

Most of all, I wondered how the team behind Urbz drew their art and what kind of technique was used. It does not seem to me to be a "handmade" kind of pixel art:

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I also searched for the development of an isometric 2D game engine. It seems that a popular technique is drawing the map from an isometric tile set (as shown here by eishiya, for example). However, the team at Griptonite Games seems to have used several large maps like the following:

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Or do I understand things wrong? What kind of engine / technology have you used?

Thank you for reading this post (and maybe for answering)!