Front derailleur angle

Hello!

I’m ordering a front derailleur Shimano Deore FD-T6000 for a touring bike 3×8 speeds (42/32/22 chainrings) and I can see that there are three different options.

• High clamp vs low clamp, which one must I order? Low clamp is better for more water can space?

• If the recommended is the low clamp one, 66-69º or 63-66º? What mean this angle?

Thank you for your help!