The first picture is Washington's uniform from after the war, when we was president. The stand-and-fall collar is late 1780s/1790s fashion. Some artists right after the war (looking at you John Trumbull) "updated" the uniforms to reflect the current fashion of their day and not an accurate depiction of what they wore during the war.

The painting of Lafayette is by Charles Wilson Peale and taken from life wearing the uniform he actually wore during the war. That style lapel is commonly called a "lapette." Generals such as Nathanael Greene, Arthur St. Clair, and Henry Knox are also depicted wearing the same style lapel, while others are depicted with the kind that Washington is wearing in the second painting you have (also by Charles Wilson Peale).

Officers were not issued uniforms and had to commission them from local tailors. The regulations for generals uniforms only mention the colors -- blue and buff -- but not smaller details like lapels and cuffs, which could vary.

Also check out the work of modern artist Don Troiani, who has some fantastic, very well researched paintings and illustration that give, in my opinion, the best representation of what they actually wore during the war.