|I don't worry about PC settings as they have no effect on bandwidth. When I monitor for bottlenecks I do so on uplink ports of switches (ie: where the fibre optic backbone connects - and in a few limited cases, where connected with copper).|
I know of no tool, other than ones provided by switch vendors, that allow you to do this.
As for physical limitations, you have them and need to know what they are.
For instance, where I work, our backbone is 10 GB capable fibre optic. The backplane of our dual redundant core switches is also 10 GB. However, our backbone is running at 1 GB because our switches in the closets operate at a maximum of 1 GB.
We upgraded the backplane on the core switches for future expansion. At this point in time, 1 GB serves us quite well. All switches are also 1 GB capable to the desktop.
With 1 GB capability, we have very little bottlenecks. Keep in mind, bandwidth is NOT a speed rating, like mph, or kmh, but is instead, a measure of the amount of data that can flow past any one point in a network in one second.
I have many many users within our main site who connect to big databases and 1 GB as I said, is more than enough for our present needs. In fact, 100 Mbps served us quite well up until recent expansion.
A properly planned and deployed network utilizing 1000 Mbps (1 GB) technology should be pretty much bottleneck free unless you have a much larger environment than where I work, and ours is big.