On Payments you can disconnect the connected Stripe account. That stops new checkout until you connect again.
Existing completed donations stay in Donations, Supporters, and Reports
Payouts already in Stripe follow Stripe’s own dashboard
Widgets and campaigns are not deleted
To use a different Stripe account, disconnect, then Connect Stripe and complete onboarding for the new account. Do this during a quiet period and take the donate page down until charges and payouts are enabled again.