Use culture to go faster. When people know what’s expected and what to expect, when they know what’s acceptable and what isn’t, they can make more quick decisions by themselves without consulting others, and they can call out others who are acting contrary to expectations.
Use process to slow things down where there’s greater risk and either the culture or human nature would not produce the desired behavior. Process to write down their justification for a request, to show their work, or to get approval from someone else who inspected their work. This helps to ensure that mistakes are caught early.