I am adding ipe 1x4 slats to the front of a brown pressure treated wood retaining wall. I will attach the slats to the 4x6 posts of the wall.

1. Any recommendations on fasteners? Is it a good idea to use hidden deck fasteners in this application?

2. The wall has two angles (see photo). I will need to either cut mitres or angled butt joints in the ipe slats to connect. Any recommendations? Would you add screws to these joints?