If you have no Analogs in your system, you should care about 2 main things:
1- Output capacitor of the SMPS.
To be sure that no possible cumulative Drain pulse of your IC's exceed max output current of your DC-DC converter. Say, your SMPS has max current as 1 A. Also your VDD is 5 V so max output power should more than 5V*1A = 5W. Calculate the sum of Max drain pulse's of your IC's, If they exceed 1 A, you should look for another SMPS which provides more than 1A. And if your total current is around 1 A, you should choose a proper output capactor which can provide you enough current when SMPS can not deliver you that much current.
Also, you should examine the frequencies of your IC's which has high current pulses. You know the equation \$ d_V/d_t*C \$ of the capacitor. You simply ough to use it. If your IC needs 500 mA in 0.1us(switching around 1 MHz) and max ripple you can afford is around 0.2V than equation is simple as this: \$ 0.2V/0.1uS * C = 0.5 A \$ so Capacitance value should be more than 25 uF. Of course, you should examine all the IC's like that.
2- Bypass capacitors. Like above, examine all the IC's with big current pulses and their frequencies. And put bypass capacitors to each IC's VDD pins with needed capacitance values to bypass others frequencies. Ceramic capacitors have ESL equivalent series inductor so each ceramic capacitor(XR7 series are suitable for bypassing) is has minimum impadence for spesific frequency. Use the correct ones.
You can also use decoupling method for high drain pulde IC's however, this complicates the circuitry much more and hard to determine ripple factor with so many decouplings. But it is only my opinion, I avoid to use decoupling unless it is so crucially needed to use( generally with one high drain pulse IC's have more than a few amperes).
however, if your cumulative drain pulse is lower than 75% of max current of SMPS, you are fine. USe the recommended output capacitor in the datasheet. So if you examine all the IC's in your system as above pointed, you will be fine I think.
One more think, SMPS's are usually used for mobile(energy efficiency is important) devices. If you have concern about energy efficiency, LDO's are more convinient to use.
I hope I could help.