Can switching regulators cause interference on wifi based circuits?

I am not an electronics engineer but it is correct to say that SMPS are inherently noisy. Linear Regulators, when properly designed are not.

That said, applying proper filtering and EMI reduction are key to proper product design. A good example is smartphones. They have multiple SMPS cohabiting with WiFi and other radio frequency devices all on a single (and tiny) pcb.

Generally speaking, PS requirements are based more on power and heat dissipation than EMI because you can always filter out noise but you can't eliminate heat.

Not sure if this helps or not...StackExchange or EEVBLOG Forum is probably a better place for this question.