My wife and I are new to this but even with our limited experience consider safe words vital in all situations, you just never know. We have 3 different safewords at the moment.

One for all stop. This is for general safety and when used a scene stops instantly and any restraints are removed.

One is for limit reached. We are still learning our limits and what we enjoy so this one means a soft limit is reached. It cant be used to lower pre estabished limits but means we can play safe without needing the all stop safeword.

The final can be used by whoever is the sub (We switch) when they want to raise limits further.

We will probably find the last two are dropped over time but for now means we have a safe fun time.