Rather unfortunately, and despite the fact that the Metro interface is significantly downplayed in the mouse-and-keyboard version of Windows 10, you sadly still have to go into PC Settings to tweak a lot of settings.
Some settings, like Power and Sleep, can be modified from both PC Settings and Control Panel. Ditto Mouse and Touchpad; change the number of lines to scroll with each move of the wheel, and it updates in both control panels.
For the most part, PC Settings is just a simplified/cut-down version of Control Panel (which is actually kind of nice) — but in some cases, it’s still the only way to change some settings, such as the new notifications/toasts, the lock screen, and tweaking finer details like “downloading over metered connections.” The worst bit, though, is that the old Control Panel doesn’t link into the new PC Settings in any way — search for “lock” in Control Panel, and all you get a link to the ancient screen saver settings.
Hopefully, by the time future Windows 10 beta builds arrive, Microsoft will ensure that Control Panel has every option that’s available in PC Settings (i.e. PC Settings is just a subset of most-used/most-useful settings) — or, at the very least, update the Control Panel search function so that it can link directly to PC Settings.
