MAC settings on The Things Stack are configurable per end device. See the MAC settings guide for instructions.
Devices migrated from V2 (The Things Network V2 or The Things Industries V2) are configured with an RX1 delay of 1 second, by default. In all The Things Stack deployments, the recommended RX1 delay is 5 seconds to accommodate for high latency backhauls and/or peering with Packet Broker.