So I finally finished the valve cover gasket install on both sides. Did everything in sequence and torque. Used sealant in the right places. I don't think the VCs are leaking again, but checked under the car and still got a couple of drops leaking under the car. I'm using 10w30 high mileage syn/blend.

For one, I'm still getting some white exhaust smoke when stopped...and also checked my oil today after going about 200 miles...and I had to add about 1/4 quart since Friday. I also cleaned up the engine the best I could, but I know there was an insane amount of crud on the exhaust manifolds.

What are some other potential leak areas I'm missing here? Though I'm mostly more concerned about this oil burning considering sometimes I can drive 500 miles on the highway in a day.

I'd suggest really spending some time with a couple of cans of foaming engine degreaser. Once everything is squeaky clean, you should any new oil leaks. 1qt in 800 miles is pretty significant... Do you see signs of the engine burning oil - like smoke from the tail pipe, or soot on the rear bumper above the muffler?

I'm seeing clear white smoke from the tailpipe (invisible during the day, visible at night).

There's still some smoke and burning smell from engine also. I used 1.5 cans of engine degreaser during this whole process. The only part I can't reach too well is the exhaust metal directly under the valve covers. Can kind of stick my hand in there and wipe it.

The leak isn't as bad from what I can tell. But annoying non the less. I'm also gunning it: Doing 90 mph sprints here and there.

Update: seems like the gasket has broken in, and no leaks/smoke. There’s like 1 drop, and still some oil burning...but no smoke or anything to do with the Valve cover.

White exhaust is likely just water vapor. Oil burning in the engine tends to be darker blueish smoke, most noticeable at startup, and under heavy acceleration.

I wanted to say, I typically don't see new valve cover gaskets needing a break-in period unless something went wrong: broke a bolt, stripped a thread, have a warped/scratched valve cover.
To check the valve cover gasket is easy, you just wipe with hand or paper towel directly below the VC-to-engine head line. If it leaks beyond that, the oil typically ends on the exhaust manifold, and you'll smell that for sure.

I haven't ever seen A VC gaskets leak so badly to leave daily drops under the car. That area of the engine simply doesn't experience that kind of pressure to lose 1/4 qt of oil per 200 miles. Not saying it's impossible, but I don't see a Nissan design that would allow that. Gravity wins here.
Side note: I don't know if you've since kept up with checking the oil levels. An estimate of quarter a quart by dipstick might not be the best. Check the car in the morning cold over a longer distance to see.
Some manufacturers state that oil burning might be a phenomenon of normal operation and that a quart per 1000 miles might be normal.

Then, check right under the crank pulley and where the oil pan meets the transmission bellhousing for dampness. These are the locations of the crank seals and you might see the drops directly underneath that if you lay a cardboard box under the car.
Keep am eye on your power steering and transmission levels as well

Well, I am still keeping an eye on it. It’s probably burning about 1/4 quart every 300 miles. But maybe I need to drive more normally and see how it fares. I just love how I can breeze past Mustangs and Camaros and not even be at 3,000 on the RPM. I had to leave it home this holiday, that car could of got me in trouble lol.

But the valve cover change did reduce the leaks/smoke from the hood. At one point it was so bad, I seen a fog of smoke emanating from my engine at night under a street light after driving for 20 miles or so. But I think overfilling it a bit kinda contributed to that. But even after getting it to the proper level, it would still smoke after a long ride. I had no choice but to drive it that way for 2,000 miles until I got home.

But I am concerned there may be another smaller oil leak in there. Crankcase seal sounds familiar. Upon buying the car, The valve cover leak was so bad, that the compressor was caked (and failed) the power steering pump was caked (that failed too)...and it was on its way to destroying every part of the engine possible. After 2 cans of degreaser and hosing down, the engine does look better.

As an aside, I realized I did the valve covers on my Maxima a year ago all wrong. I thought I was supposed to put RTV around the whole gaskets. Checked the other day while changing plugs and boots...they’re both leaking. I am so mad, but the smaller sized 3.0 engine is a bit easier to reach than the massive 4.0. However, the rear valve cover is an absolute PITA to get to.

This time, I skipped on rtv and just used gasket sealant in the places where it said to use RTV.