for the kick back noise of bandgap, u may use RC to reduce (buffer is high current consumed)
for the noisy power ,u need a high psrr bandgap at about 40-50dB@ripple frequency,and power decouple cap is necessary。as to layout u need seperated the power line of digital and bandgap。 above solution is enough ,u do not need so many redundancy circit block cause of not much improvement and current consumption。
u first figure out some concept,the giger Hz noise and low fre noise is killed out by decoulpe cap and high psrr of bandgap,only the medium fre is you care about.and the medium fre psrr of bandgap is not only depend on bandwith of bandgap.you first figure out the psrr of bandgap of all the fre.