question

The part numbering (150/35) is the maximum pv voltage (150) and the maximum charge current (35).

20% over on panels tends to be ok (sometimes advised to allow for sub optimal performance of panels) but any more and I would be changing controller.

If you look in the data sheet you will notice the nominal solar values.

For 24v it is 1000w which means you could run 6 x 200w panels (1200w) and have the output capped at 1000w.

For 48v you could happily connect 12 panels.

If you connect 18 panels to the controller it will still have a maximum output of 35 Amps so would be wasting a lot of capacity and depending on how the controller works, could have to dissipate some of the excess as heat.

Yes, you’d definitely want to watch the voltage coming in. Some 24V 200W panels can have an open circuit voltage over 40 so adding very many of those will have you over the incoming PV limit in a hurry. I was originally looking at the 150/85, but changed to the 250/100 to give room to roam. I have 4 x 300W panels on in series, with room for 2 or three more, if needed, more if I break them into parallel arrays. In the end, I am keeping charge power under well under the 100 amp limit so more is not that beneficial.

As noted in the other answer, the 150 is an incoming voltage limit, and the 35 is the outgoing amp limit to the battery bus. The SCC will convert any incoming voltage over your battery setting (~26.6) to increased amperage on the output side. In other words, if you’re nearing that 150V incoming limit, you’re likely well past the 35 amp output and the SCC will not use that power unless your loads are drawing it off. That‘s why it’s always so important to match your SCC, Inverter if used, panels, and battery bank. They are most efficient when matched.