The issue you're mentioning with Repeater is probably caused by switching windows with the default global hotkeys. If you don't need the hotkeys global (as in, you can be typing in your browser and hit Ctrl+Alt+1), you can probably specifically set the hotkey to Ctrl+Alt+1 etc in your Character Set slots, and the problem might go away.

It's interesting you mention latency with key maps, as it should be identical to using Repeater. The difference is that Key Maps allow you the option of holding the keys while you hold it (which would be identical to Repeater, where press/release takes effect when you press or release the hotkey), or doing a quick press+release when you release the key. If your issue is timing, it sounds like you have the Hold option disabled for your mappings, and things may improve by enabling it.