Initially I shared your concerns with regard to the smaller zone 4 area, having had it a good while now I find I can do several whole chickens on it or a twin pack of pork butts with ease. The upper rack (zones 2 & 3) have a bunch of space as well I have done an extra two whole chickens up there and just kept an eye on them as they finished 20 minutes sooner.
You can load every inch of it without worry, the entire surface heats evenly and that's just not the norm for any grill I ever used no matter the heat source.
I love the way it cooks set to 225* for long cooks doing briskets etc, it is the definition of true low and slow on account of the lack of any radiant heat and it actually takes quite a bit longer using my old tried and true 225* recipes on account of it but you'll never burn anything on it and the moisture levels left in the food after a good rest make for world class BBQ.
The charbroiler will actually hold 4 nice 1.5~2" porterhouses or similar so don't let that hold you back it's plenty large for a family meal.
Here's some photos of the cooking areas, helps to grasp the scale of things with some food for size references.
Costco brat's and 1/3 pound burger patties, (these are really tasty if you can get them btw)
You can put six loaf pans of your favorite sides up top in zones 2 & 3, or 2 dozen ears of corn easily. Those are large racks of baby backs that touched the ends of the cooking grates front to back when I put them on.
Half chickens in zone 4 are to die for, 5-6 pound broilers at 300* are ready in 2-2:15 hours crispy smoked skin and the meat is tender and full of juices.
Best brisket I have ever cooked, hands down best taste and the most moisture it was a Costco 12 pound prime trimmed to 9 pounds before going on overnight.
Like any new grill or smoker it takes a little time to get used to how it works, but with the user programmable controller settings you get to dial it in to suit your needs according to fuel quality, weather conditions etc. and it holds set temps right on the money.
I'd buy it all over again, having it and a proper thermometer to use with it has made me a better cook. I ordered mine from Dan at Firecraft, he ran circles around most of the product rep's I spoke with during the selection process when I was looking at different models he really knows pellet grills and smokers inside and out.