Is it possible to connect two GPIO screens to the Raspberry Pi at once?
Ideally, one with touchscreen capabilities and one without.
If it's not possible, could both a GPIO screen and a small HDMI screen be used instead?
It is possible to connect more than one display, if you have enough GPIOs. But most screens use SPI and the RPi has only 2 Hardware SPI CS signals.
You can also use the video output or HDMI for the 2nd screen.
I think you can do it via i2c interface, if your screen uses one, or if not - you could build a spi to i2c bridge for it.