a. It depends on the specific trunk bag and the type of mounting system it uses. Some trunk bags use a rack-mounted system that attaches to the seatpost, while others use a strap-based system that attaches to the handlebars or seatpost. If the bag uses a rack-mounted system, it may require a clear line of sight for the mounting hardware to work properly.
b. It depends on the design of the trunk bag. Some trunk bags are designed to be mounted horizontally, while others are designed to be mounted vertically. If your trunk bag is not designed to be mounted horizontally, it may not work properly or may not be secure. Additionally, if the trunk bitlife bag has a built-in light system, mounting it horizontally might obstruct the lighting. Check the manufacturer's recommendations for proper installation.