Provided both cabs are rated at the same impedance, they’ll be getting an equal share of the power, regardless of whether you’re daisy chaining or have separate speakon/jack outputs on the head. The head also doesn’t care what the cabs power rating is - they’re getting fed the watts whether they like it or not.
It may be useful to think of the impedance of a cab as the sum of its speakers where Ohms are concerned. For example a 2x10 rated at 8 ohms will be made up of two 16 ohm drivers which, paired together, equate to an 8 ohm load. If the 2x10 is rated at 4 ohms then each driver will be rated at 8 ohms. In a 4 ohm 4x10 cab each driver will be rated at 16 ohms, etc.
This is why it doesn’t make a whole lot of sense to stack an 8 ohm 2x10 on top of an 8 ohm 4x10 as the drivers in the 2x10 will be working twice as hard as those in the 4x10 and you’ll have a bit of an imbalance. In this scenario, as far as distribution of power is concerned, the solution would be to have an 8 ohm 2x10 on top of a 4 ohm 4x10. Trouble is, not all heads can handle a load lower than 4ohms total so this isn’t possible for a lot of people. Barefaced worked around the issue by developing their 2x10 cab in a 16 ohm version which allows you to stack 3 of them and only have a 4 ohm load presented to your amp. It’s a Class-D friendly solution. 3 Barefaced Two10s ain’t cheap though