Geberit Toilet Installation

I'm considering the Gelebit pressure-assist wall mount toilet for a basement installation. I would use the horizontal discharge option.

Questions:

1) Along the wall, the optional horizontal disharge elbow and the spec shows a 45 degree angle down before going horizontal. From your experience, is this necessary? Could the supplied straight elbow be used for direct horizontal drainage along the wall; using it to the side rather than straight down?

2) Do you think a gravity swing check valve on the drainage line would be okay, if desired?

Kind regards,

David