The amount of charge accumulated on the CINT capacitors is important for the operation of magsense. That is why 470pF capacitors are chosen. The voltage on the CINT capacitors on PSoC no way reaches the voltage level of 50 volts. Infact it will be less than the operating voltage of PSoC (VDDA/DDDD). So you can use capacitors with less voltage rating. No problem. Same logic applies for CMOD capacitor also.
Coming to the package type, please note that there will be differences in secondary parameters like leakage resistance, inductance between 0805 and 0402 packages. However, there will not be any problem related to performance with these changes in secondary parameters if you chose capacitors from good quality vendors.
Hope this helps !
There must have been a reason for picking 50V on the ev-kits. Could it be better derating?
Would be great with just some input on 1 & 2, regarding C0G, NP0
Voltage rating: The idea is to use a cap with voltage rating greater (at least twice) than the operating voltage. Any Cap with voltage rating greater than 10 V should be fine. Since 50 V rated cap is the most available one (also cheaper), we have used that in this board. But do not use a capacitor with voltage rating closer to the operating voltage.
Dielectric: We recommend using C0G (NP0) since it has good performance (+/- 0.3 %) over temperature range (typically -55°C to +125°C). Cint/ Cmod capacitors should not change it's value over temperature as they affect the sensing performance. That is why we recommend C0G (NP0) caps with 5 % tolerance for this application.
X7R capacitors are suited for decoupling capacitors placed in the VDDx pins.