can we replace 22uf capacitors (CAP CER 22UF 16V 10% X5R 0805) placed at Vout1, Vout2 and Verfout of MC34716EP with capacitors of higher Voltage like 25V and lower package like 0402? Do we get any problem with harmonics due to higher voltage cap. please suggest.
No problem is expected with your exchange, especially if capacitors are X7R. Note that ceramic capacitors have problem of reducing of capacitance with increasing DC voltage bias. This is especially applicable to capacitors with smaller package size. However for 1V voltage this effect is not so great. Anyway, try to consult with capacitor vendor how serious it can be for your particular capacitors.
Attached a picture from Murata explaining the issue.