Converting 5V to 3.3V with 100mV ripple max, preferably without board
I would simply use the 3.3 V version of the DCDC converter modules you mention ( NCS6S1205C and NCS6S1212C), they have a 3.3 V version also: NCS6S1203C.

Then feed that 3.3 V module from the same input voltage that the  NCS6S1205C and NCS6S1212C  modules are using already, that way the two existing modules are not loaded more than they are now.

The NCS6S1203C has a 1.52 A maximum output current and 30 mVpp ripple which satisfies your needs.

The TPS60201 and others you mention are only "bare" chips, to use them you need to design a PCB for it and the required support components. That's much more work (and more risk that it doesn't work, especially if you have not done this before) than using a ready made module like the NCS6S1203C.