btw, at present I am planning to power the whole circuit with the same SMPS.
do you think i should go for another regulator just for the bridge in case i need a 0.5 deg C resolution from my application and the range I am targetting is -20 to 200 deg C?
Why is your third RTD wire going to ground? That defeats the purpose of it, unless I am misunderstanding or overlooking something. It should be the zero-current connection directly from the RTD element to your voltage amplifier (as would a probe on a voltmeter sampling a voltage drop). The purpose of the 3rd wire is to eliminate at least one wire's worth of added circuit resistance. That is, in most applications I have ever seen.