hydrolysis of ester

Basically it cannot be Sn1 reaction, so yes, please consider Sn2 reaction.

Since the rate determining step is the approach of the nucleophile, the magnitude of hte steric hindrance between the nucleophile and the side branch will be a significant factor. Bulky side branch prevents the approach of nucleophile (especially for the bulky nucleophile, such as alkoxide ion of tert-butyl alcohol).

So it's reasonable to predict that RCOOR' has higher rate of hydrolysis than RCOOR'' .