It doesn't make any difference if you install DBP in W7 or W8, it'll work the same in either.
W8 you will have to run it in compatibility mode (W7) though.
FYI - compatibility mode = rt. clk on the DBP.exe/properties/compatibility tab.
Once you set W7 as the default (in DBP) you will get the normal Vista/W7 boot menu.
You may get it (automatically) since you are installing W7 on a W8 system.
If yoou set W8 as the default you will get the grapgical W8 boot menu.
Let us know how it goes.