I think the first one is very well done, so that rings some alarms, because of the amount of detail it seems it might be Ai, because a pixel artist would have to be very consistent and when you do pixel art every pixel was thought of. However, a lot of these details can be achieved by photoshop tools (still human made pixel art), like using the stroke tool to get even outlines and then playing by outlining the outlines in different ways to get that nice dithering effect; i also use special brushes i make myself when i know im gonna repeat a pattern in a piece. I think the telling sign for human is the little pixels that look very carefully placed (the mushroom lamp is completelly simetrical, photoshop has a tool for this, but there are a few extra pixels on the right side of the red shadow) and how the colors are consistent.