1) I'm not sure if it is actually documented anywhere, but the code that generates the textures is at
psychopy.visual.basevisual.TextureMixin._createTexture (current) and the options can be seen there.
2) You could perhaps use
BufferImageStim to render a text stimulus and then use the result as the texture for an
ElementArrayStim. But that gets a bit tricky with the alpha channel, so you are probably best to just implement the
ElementArrayStim functionality manually (i.e. draw your text stimulus multiple times, updating its
pos attribute each time), if that is feasible time-wise.