Are you running AI on ALL your cameras?
You only really need it on point cameras as these tend to be high traffic areas. The more cameras you have running AI, the more processing power you'll use. The main focus of AI is to cut down uneccessary alerts. Also, consider what filters you are using. The more items you choose to identify, the processing has to happen to check all the item against all the photographs. I keep my list simple to Person, Car, Truck and Bike.
As for efficiency mode.
In the search box at the bottom left of your screen type "Control" - a list should form with "Control Panel App" in it. Click this.
This will open another list. Click "Power Options"
If it doesn't open on this, click "Choose a power Option". Click "Balanced" if it's currently in "Power Saver" , or if you want to go all out (I always do) click "High Performance". The latter will give yopu maximum performance from your pc. Don't worry about the power. I doubt you'll notice any difference.
Also whilst in the same window click "Change when the computer sleeps" and ensure"Turn off the display" and "Put the computer to sleep" are both set to "Never".
The latter won't help performance, buit will help with other issues including a known windows bug with waking up from sleep mode.
Also check your BI version for a known stable version with the builds people are using on here.