Generally the blade leveling is done through adjustments of the bed relative to the cutting head, and generally the log bed supports are individually levelable. As the blade bites into the log, it could slightly change the level of the cut. So the bed should be adjustable to the cutting head, at least in my opinion, and the cutting head made as rigid as possible. With a 2 track design that shouldn’t be a big issue, but I still wouldn’t be surprised if there is need for adjustable bed.
With a 2 track design, making one side adjustable will have the same effect. Adjustable bed sections can get distorted by dropping or moving heavy logs on them.
Whichever way, adjustment is going to be the only way to dial the sawmill in for perfect cuts.