Some larger models include multiple separate MPPT circuitry.
The Conext MPPT solar charge controller family only has a single maximum power point tracker in each unit. Multiple strings should be connected in parallel and the MPP will be found as an average across all strings.
The MPPT 60 150 has terminals for convenient connection of two strings without the need for an external combiner box.
The MPPT 80 600 has terminals for connecting up to three strings without an external combiner box (most installations will require external fusing when using more than 2 strings). See attached image for locations of PV terminals.