Re: Dual tracking
Jonathan Bernstein doesn't think "dual tracking" -- letting senators filibuster without holding the floor and stopping all other Senate business -- much matters for the modern filibuster. His argument is here.
My take on this is that dual tracking was important for the rise of the filibuster, but getting rid of it wouldn't make much of a difference at this point. The fact that a filibuster used to stop all other business contributed to a strong institutional norm against filibusters in the Senate. They happened, but they were rare. When they became less costly to mount, they became more common, and more culturally accepted within the institution. It was no longer weird to filibuster. If you removed dual-tracking today, the new norm would remain. The result would be a real inability to conduct Senate business, and thus a real problem for the functioning of the federal government, and no one quite knows how the public relations of that would play out.