advantage of second motor on y axis ?

Hi ... I'm trying to design my first CNC router with ballscrew on Y axis ... roughly 50 x 50cm cutting area.

1. Everybody seems to use 2 stepper motors on Y axis on OX type machines ... but that means 2 expensive ballscrews. Can't I use a single high torque Nema 23 (345oz) mounted in the middle of the machine or even Nema 34 instead ?

2. Can I mix Nema 23 and 34 on one machine.

Thanks