From my experience, I had 350w of panels on the roof with the Jayco PMW controller.
When I attached the 160w portable fold out panel, anderson plug direct to batteries, with it's own PMW controler, the Jayco PMW controller reduced it's charging by about 2/3 amps, mid winter, therefor negating adding the extra watts.
Upon returning home I dismantled the folding panel and installed the 2 80w panels on the roof runnning thru the Jayco controller but when parking the van with the door facing southish I get shading from the A/C on the first row of cells killing most of the power out of the extra panels.
I have replaced the 30amp Jayco PMW controller with a 40amp MPPT controller and that has increased the charging amps by 3.
In future I will be parking the van with the door facing north were possible. If I get sick of that I will move the 2 80w panels so their not shaded by the A/C.
I have a mixture of 12v panels but the voltage outputs are virtually the same which is OK to do when hooked up in parallel.
I'm also toying with going 24v with a mixture of series and parallel which will put less current load on the wiring to the controller.

I tried it a couple of days ago the 24 volt string in full sun flat on the roof 200w gave me 11 amps.
But the string that's slightly shaded started at 40voc dropped to 15v completely negating the shaded panels. If I want to go 24v I'll have to move the 2 shaded panels, I have the room but don't have the will at this stage.

You can run 2 PWM controllers on the same battery and as long as the battery can absorb the additional charging amps the two controllers will add their inputs together and increase the charging current. If the battery is already at the point it can't absorb any more current without the voltage going over the 14.4v or so the control should be set at, then there is no value in adding panels or changing the type of controller because the battery is the bottle neck, not the controller. If the controller you have doesn't get the batteries to 14.4v or better before it starts to cut back the charge current, adjust it till it does or replace it with one that can be adjusted.
As far as using an MPPT controller and adding portable panels into the one controller, unless all the panels are in parallel then it just won't work. If they are in parallel, then the open circuit voltages should be very close to the same and also need to be at least 5v higher than the max voltage you are looking for at the end of the boost/bulk cycle, 14.4v for AGM or Gel, 14.8v for flooded cell and 15.1v for calcium. If you don't have that additional 5v it is quite likely the MPPT controller will not start up at all.

T1 Terry