What will be the effect if I combine separate solar strings facing different directions on a single charge controller? Will I get the average of both outputs or less?
By paralleling arrays the current will be higher from the array facing the sun and lower from the one that isn't. That's the nice thing about putting arrays in parallel like this - the current from each adds up.
So in the morning, the east array will generate most power while west is supplying less, so yes it will be the average of the two but that's because one is getting good sun while the other isn't. It would also be the average of the two if they were each on separate charge controllers/MPPTs.
In the middle of the day they will both be contributing roughly equally, the in the afternoon the west array will generate most.
It's a really nice way to layout arrays, as it flattens out and widens the production curve across the day, reducing the peak in the middle of the day. This can advantageous, especially if the potential peak output from a single orientation array is higher than your system can productively use.
Since both arrays are connected to the same MPPT they will be operating at the same voltage, so that will be a little sub-optimal compared with having separate charge controllers or MPPT inputs, but a decent MPPT will still settle on a voltage which generates the highest power output overall and because one array is facing the sun the voltage will naturally favour the array with the best production conditions. It might be you lose some production potential from the array not facing the sun, but since it's only going to be generating a minor contribution at that time anyway, you're not losing much overall. It will represent less than a handful of % compared with having separate charge controllers. Usually just having a slightly higher rated panel is more than sufficient to make up for any small losses.
My only suggestion when paralleling arrays is for each string to be of the same number of panels of the same rating. So e.g. use 3S2P, or 2S3P but not 4S+2S for instance.
If 3 or more strings, you need to fuse each string before your parallel junction.
And fuse/wire for max possible amps at any one time.
This.
A combiner box can make the task easier for combining more than 2 strings.
And of course make sure about voltage for the strings being connected are suitable for the charge controller's limits.