How to decide the number of SI and MI of SmartConnect ?

Hi,I am using the hdl release 'hdl_2019_r1'. And I am using the project in zc706 .I want to know how to choose the connection of MI and SI .

In the reference design the 'S_AXI_HP0' connect to 3 SI through smartconnect. but the 'S_AXI_HP1~3' only connect to one SI each.

Can i connect the 3 SI to 'S_AXI_HP1' through smartconnect ?

Why choose different connection style? How to make a decision?One reason that should be considered is the bandwidth of the S_AXI_HP or SI,I guess?

Is there any other reason that should consider? Help me please.Thank you.