I have a 400Mbps down connection. I've purposley capped my PC to only use 300Mbps so other devices can get 100Mbps to use. The problem, I am having is that when downloading on my PC at this max speed

For example, if I have one MAC set to high priority (60% bandwidth), but it only needs 10% at the time. Will my other devices be able to use part of that 60% until this one MAC actually needs it? My d