Just look at this and wonder can you use more than one at the same time ie. ic2 address changes the pHAT your pcb says x70 but can it be changed so that I can use 2 or three together (power being supplied external to the PI.
2nd quick question (and I except that his is a PI biased product) as it is a IC2 system could it be driven by an Arduino. which with the correct code to send the character to each of the segments,
The I2C address for the chip is fixed, so the short answer is no, you can’t use more than one.
The long answer is that it should be possible to use the secondary I2C0 bus on the Pi to drive a second unit, though that would require hacking the python library (or custom program, in whatever language works for you).
And sure, you could use an Arduino. To drive the HT16K33 chip I would have a look at: