As long as the chargers' voltages are above the battery's voltage, each charger will supply some of the total amps. How much each supplies is in proportion to its voltage difference.
As the battery voltage rises from being charged, amps will start to taper from the lowest voltage charger of the three until amps get to zero when the voltages are the same, then amps will be tapering on the next highest voltage charger until battery voltage rises to its voltage, and now only the highest voltage charger is supplying amps (to its current limit).
Then, as battery voltage rises, it gets to the absorption voltage for the highest voltage charger so amps taper from it till the battery is full.
If you want the three chargers to add their amps to the highest amps total for the longest time as battery voltage rises, you have to set the charging voltages of the three chargers to as close they can be set, and to the charging voltage spec of your battery.
EDIT--just to make it more fun, the chargers' voltages are as seen by the battery at its end of the wires, so voltage drop is in there too.
The alternator has its own ideas about charging voltage so in real life as it starts at 14.x and then soon is at a lower voltage while you are driving, it could be the lowest voltage and you won't get as many amps from it as you might expect.
The converter could be problem too, where it could be doing 13.6 instead of 14.4. Depends on the converter and its wiring what happens with it. Might not be worth the generator gas to use the converter at all, depending on the converter's voltage.
So if you are hoping to get lots of amps by using all three chargers, you could be disappointed, but it won't hurt anything to have them all on at once, except if you go over the battery specs for charging voltage and current.
You can beat the alternator voltage problem by using a DC-DC charger instead. With that, you can choose a voltage from it's menu and it holds that constant (buck /boost converter in it) and it does its rated amps constant until they taper in the usual way. So with that you can match the solar controller's voltage and maybe the converter's.
You can beat the possible converter problem by using an adjustable voltage one like the PowerMax LK model.
So then you only have to choose the current limit amps size of the converter, DD-DC charger, and solar to be under the battery's current limit. ( 1C max or 0.5C recommended for some 100AH LFPs, eg.)
