The Resolution attributes can be found in both the bifrostAeroProperties and bifrostLiquidProperties attributes.
Typically, you use as high a value as possible, depending on the scale to which the scene was modeled, to get a fairly quick preview as you adjust various settings. However for an accurate preview, the value should be smaller than the smallest feature of the simulation. For example, if you want liquid to drain through a 0.2 unit hole in a collider, then Master Voxel Size should be 0.1 or smaller.
Once you are satisfied with the overall simulation, you can decrease Master Voxel Size to render the simulation or generate a mesh at a higher resolution.
For liquid simulations, you can further adjust the voxel size used for collision, acceleration, and guides relative to the Master Voxel Size by setting the Voxel Scale value in the corresponding attribute group of the bifrostliquidContainer.
For aero simulations, the Master Voxel Size controls the resolution of the voxels used to simulate the FLIP particles directly, and is also used in conjunction with Voxel Size Render Factor to determine the resolution used to advect the render particles by the FLIP simulation.