I run 38mm tires on 23mm rims (17.5mm inside width). The tires are labeled for 45psi, but I usual put the rear tire pressure around 55psi (combined bike and rider weight being ~180lbs). Below that the rear tire feels a little loose.

Low pressure affects the handling just as much as low pressure on a narrower tire. Personally, if i wanted lower pressure I'd get wider tires and wider rims.