The later versions of p5 1.?? use webgl 2. I haven’t started doing anything with p5 2.0 yet.
Webgl 2 is based on OpenGL ES 3.0. If you google for “gles 3.0 texelFetch”, for instance, the khronos documentation pages, such as https://registry.khronos.org/OpenGL-Refpages/es3.0/html/texelFetch.xhtml, will show you what versions of OpenGL ES support a given function. Webgl 2 supports integer types including the gl_VertexID integer value which I use throughout my code.