so we were wondering that since NXT motors are allowed, are LEGO technic pieces also allowed?
For which competition? FRC? FTC? FLL?
If FRC: yes on the hostbot assuming they are COTS (see <R27>), but no on the minibot (see <R92>). There’s a crafty little exception for any Lego parts made from polycarbonate (like some of the transparent ones), because <R92> allows polycarbonate in any form. However, most opaque Lego bricks are made of acrylonitrile butadiene styrene (ABS), which is prohibited on minibots.
Yeah its for FRC, and do you know if you can use LEGO axles and wheels for the minibot?
No, see the rules quoted above.