Immediately for browsing and cart rules: the next page the member (or manager) opens uses the new switches, including which modules the member may check out in and whether extra meals/extras are shown. The payer of a subscription, however, is fixed when that subscription is created — the subscription itself stores who pays (based on You pay this member subscription at the moment it was set up), so turning that switch on or off later changes who pays for new subscriptions, not renewals of an existing one. Also, if the member already has items in their cart, the cart keeps the payer setting it was loaded with until the cart is reloaded.