Excess Geometry Questions

Hi, Johnathan.

Loving the blocking section of the course so far and I have already learnt a few tricks for later use. However I just have two questions to ask about potential excess faces

1. At 1:39 of the video, faces that were beside the edge of the model to the right were deleted to lower the poly count. This technique, I found, was solemnly used for the other models where they connected against each other (for example, there were faces on the back of the trigger model that weren't visible). Would it be acceptable to selectively delete these faces to save more geometry or keep them in?
2.  At 4:51, you used an edge loop to add more geometry to the handle then used an edge slide to move any excess vertices down (and removed them using remove doubles). Would the same technique be allowed during the creation of the edge loop during 6:47 of the video to remove the excess geometry created from the edge loop around most of the handle?