Can a dual extruder printer print with multiple filament types?
Yes and No
Yes, if you have two full hotends, you can easily print with two filament types.
Yes, if you have one hotend and both filaments melt at a very similar temperature or are the same polymer, then you can use a Prusa MMU style or splicing machine.
No, if you have only one hotend and the two materials are very dissimilar in their print temperatures (PLA with 200 °C and ABS with 235 °C), then you can't use a MMU/splicing style printing. This does preclude PLA and PVA from the same nozzle: PVA needs about 230 °C according to my data.