Since denon x1400h has only one HDMI out, by default you can connect only one output...either your TV or projector. Only workaround is to use HDMI splitter as suggested by
@MaSh above. You can search for good HDMI splitter in this forum or do an online search and select one which has good review. One with remote will make your life easier.
With regard to inputs, you can use any of its 5 HDMI inputs. HDMI labelling (cbl/sat, Bluray etc) are for convenience and easy identification.
If you are planning to use your tv's smart apps (YouTube Netflix etc), do enable arc on your TV, to get sound from your TV to receiver.
Enjoy your new receiver...