In general it is just a personal choice. Bare bottom is fine and deep sandbed is fine. So in-between will work. If you are planning to keep wrasses that sleep in the sandbed, it is better to have a deeper sandbed, or at least spots in the tank where it can easily dig in. When it comes to maintenance, bare bottom is the cleanest and easiest, however with a deeper sandbed there is theoretically more area for anaerobic bacteria to grow and those will reduce nitrates in the long run. For me personally, I highly doubt that this is a reality in the hobby. Imo it is more work to clean and it’s a good place for detritus to build up if not well maintained and I have seen no significant evidence of nitrate-reducing properties.
I went for 2,5 inches and keeping an ornate leopard wrasse