MacOS – Suddenly when I hold down arrow key it takes a moment for OSX to respond

Here's how you can get ⌃ Control+arrow keys to work like you describe. Copy the following property list into ~/Library/KeyBindings/DefaultKeyBinding.dict (you can create the directory if it doesn't already exist):

{
    "^\UF703" = ("moveWordForward:", "moveWordForward:", "moveWordBackward:");
    "^$\UF703" = ("moveWordForwardAndModifySelection:", "moveWordForwardAndModifySelection:", "moveWordBackwardAndModifySelection:");
}

This will set up ⌃ Control+arrow to navigate to the beginning of the next word (by using OS X's normal navigation three times: to the end of the current word, end of the next word, then back to the beginning of the next word). I also included a version that works with ⇧ Shift so you can select text as you go.

Caveat: this will only work in Cocoa apps, but I think the normal ⌥ Option+arrow navigation does too. Also, make sure to relaunch your apps!

An ideal solution would be a single key press that is relatively intuitive and consistent with other keyboard interface rules. Nonetheless, I have found a couple of hacks that seems to work.

• Cmd+[ then Cmd+]: This navigates back then forward. After this has occurred the focus is on the file list. A mild nuisance with this option is that the search is refreshed, which can lead to a brief lag.
• Cmd+Shift+G followed by escape: This opens the go to folder dialog box; escape exits the dialog box and returns focus on the file list.