You can use both. When you have the center differential unlocked, you aren't really in 4wd, you would be in AWD. AWD allows the wheels to spin at different speeds while turning without having to slip or scrub, but it still routes power to the front tires so that you can drive with confidence in rain and snow and avoid having your front end sway or lose control.
When you lock the center differential, you are in real/true 4wd. This allows for a true split of power between the axles, but is not to be used on the road because the ample traction doesn't allow tension to be released from the drivetrain like it would be in normal off road conditions.
The E-locker and the Center locker can be used at the same time, it would be just like having any other part-time 4wd vehicle in 4wd with a rear locker engaged. And as long as your install doesn't somehow disable the ATRAC functionality, that should work too without issue. This is ideal because you can lock the rear axle to a true 50/50 power split between the two rear wheels, while still having what is essentially a limited slip differential functioning in the front axle.