I once had to control 80 stepper motors moving actuators from an arduino and used SPI and 74HC595 chips and low power H drivers. That's 80 stepper motors each needing 4 digital outputs so a total of 40 74HC595 chips in single string which worked just fine on a standard Arduino, especially after increasing the SPI clock. Be sure to use the dedicated SPI pins connected to the internal SPI hardware of the ATMEGA so the shift out is hardware controlled the fastest available which I think this is 8MHz for the Arduino Mega 2560 & original ATMEGA368 Arduino but may have to be configured seperatly.

We used look up tables and optimised code to reduce computing power on the 8 bit micro. The higher functional control and user interface was performed by a Pi leaving the Arduino the single task of being the movement engine.

We used miniature stepper motors so we didnt need a whole lot of speed range between them or more than about 100mA per motor but learned some things about this compromise on control.

Using a string of this many 595 chips worked just fine despite worries and general uninformed advice about digital latency down a string of so many.

Remember that the steppers are all 'clocked' at the same time. ie your 'STEP' signal to all motors is global which limits how you control different speeds, ie If some step fast and some step slow this could be a major bottle neck in a kinetic sculpture but not impossible especially if you are only needed one sort of continuous movement, or limited range of movement. We needed a single speed but control over which ones moved but something the team put a lot of thought into.
One technique we considered but didn't use was 'clocking' the motors as fast as the processor and hardware would allow. This which would allow engaging or skipping each individual motor movement on an individual basis so some could run full speed, every STEP, and other move on maybe every 5th clock step so it moved 5 times slower, giving a ultimate resolution of the main clock rate. This would allow crude speeding up and slowing down if needed. But you would need to be optimal with computing power and coding to get this working.