1 st order are inherently stable but noisy
2nd order are less noisy and C2/C1 ratio affects pole position
3rd order are inherently unstable with >180 deg phase shift and negative feedback becomes positive feedback.
Rule of Thumb ratios help provide LPF additional rolloff using lag-lead filters to give phase margin at unity gain and may have less jitter.
So, if I design the additional pole carefully , and the additional pole does not degrade phase margin very much
it is alright even I don't follow the rule ?
(i.e. R3 < R2 ; C3 = C1)