Re: what is the difference "spiral_std_mu_z" and "spiral_sym_ct_mu_z"
spiral_std_mu_z are the normal inductors in the ultra thick metal layer of the process whereas spiral_sym_ct_mu_z are the center tapped inductors which are symmetric about the center tap, which is also in the ultra thick metal of the process.
If you are doing a single ended LO buffer design, you have to go for spiral_std_mu_z. If you are doing differential design, then you can use either one.