I have two Let's Play recommendations for you, however neither is for your preferred systems. They do however showcase well how fiction and mechanics interact.

First recommendation is one of the many solo plays of Ironsworn, or some other solo RPG. Since there is only the player and the game they have to rely on mechanics much more than if it was played in a group. Also since there is just one player, who also GMs, we tend to get insight into how they work with the rules. The Let's Play I'm going to recommend is one from Me, Myself and Die. It is also one of the more recommended ones with good production values. https://www.youtube.com/playlist?app=desktop&list=PLDvunq75UfH_Z92nrYPUsTO_fTHnLTNaT

Second is for the Dungeon World gack Stonetop. At this point calling it a hack is making it a disservice as it have evolved into its own thing. The DW ancestry is clear though. This Let's Play is from the creator of the system with his core playtester group. What makes it stand out it that it is really well edited cutting out plenty of non-play filler. In addition to that the editor have annotated the videos with comments about the mechanical choices the GM makes. Good for following along. https://www.youtube.com/playlist?list=PLDdTGJVXI31C08Kem-oLzXqRgImtLzXKC

Hopefully this will be of some help.

*Edit: Updated second link. *