Test Print for Dissimilar Supports

When printing a model that requires support scaffolds, the default is to use the same material for supports as for the model. This is because the majority of consumer grade 3d printers have only one extruder. But we observe in recent times increasing numbers of dual/multiple extruder printers such as Prusa XL, so the possibility increases of being able to make 3d prints having one material for the model, and another material for the scaffolds, making use of the fact dissimilar materials often do not stick permanently to each other and are more easily separated.

I'm sorry if your patience is tested because my style is verbose, but its a deliberate move to spell things out, to achieve better communication. Read it or not, your choice.

So, when printing using the same material for model and supports  you often find those supports stick strongly to the model, becoming difficult (and unsafe) to remove using a craft knife. Furthermore the lower supported surface of the model is of degraded quality. You seek to mitigate those effects.

So, folks turn to using another material for the support scaffold, allowing for easier removal.
The support material falls into 2 categories:
a) Soluble type: PVA, PVB, HIPS (and other specialised material) which are often relatively expensive.
b) non-soluble type, chosen mainly to be of the less expensive materials such as PLA.

Whichever support material is used, the goals are to:
a) have the support material stick to the model material particularly on the first layer of the model, and ON completion of printing, the support material needs to be easily removed from the model by mechanical or other means (such as dissolution).
b) have the support material stick to the selected bed during printing, and be easily removed from the bed upon cooling.
c) the support material needs to have sufficient strength to act as support.
d) achieve the least expensive support option. Solubles are well and good, but are highly priced, and generally only work with a few model materials. Ideal world would see cheap PLA supports for all the higher end materials.
e) achieve a decent printing speed, allowing you to maintain a competitive cost overall.
f) not to introduce unwanted effects such as warping of the model. (this model does not test this aspect).

The problem is that the support material needs to have rather specific qualities relative to the model material in order to achieve the goals. Not just any material can be used to support any other material.

The filament manufacturers supply scant information about how well a given material sticks to another.  Some do, some don't supply a support material product that works.
The user is left to their own research to discover a combination that works. 

So, herewith a very simple model designed to achieve the required discovery.

Important and relevant Slicer settings focused on the goals: (and set in the supplied Prusa Slicer project file).  Hint: The essential secret sauce is a RAFT and 0 top contact. And don't go overboard with the print speeds.
(A conservative approach taken).
Prusa Slicer > Print Profile
0.20 mm Layer Height, Balanced profile.
RAFT layers: 4.  << The goal of having a raft is to have only support material in contact with the bed, for consistent optimal bed adhesion.
Support Options:
- SNUG. Others might work too.
- Top Contact 0 mm. << to achieve best surface on the supported model.
- Top interface layers 1 (light)
- Bottom interface layers  0 or 1 as needed.
- Synchronise with Object Layers: ON

Multiple Extruders:
Perimeters, Infill, Solid Infill Extruder = 1 (model material)
Supports, Wipe Tower, Bed Temperature Extruder= 2 (support material).
Wipe Tower: Enabled (with other settings default).

(Hardware: Same nozzle type and aperture for both extruders.).

Filament Profile:
Use Your normal nozzle and bed temperature settings for the material.
Extrusion Multiplier calibrated.
Dry the filament !
Maximum volumetric flow: conservative. Slower is better for this test.
Cooling: take care to set optimal cooling for the material. Consistent Surface setting.
Filament Overrides: Retraction, Retraction Speed and Lift all set to minimise stringing and plastic accumulation on the nozzle.

There are a wide range of materials.  Ultimately the goal is to create a grid matrix of compatible materials. The term “compatibility” mainly refers to adhesion of the one material to the other during printing. (Ideally) The track of lines on the first model layer remains true, not out of shape compared to Prusa Slicer preview.

Noting that Generic materials from different manufacturers often have differing characteristics due to proprietary formulation. Heat Flow and Adhesion characteristics of material can differ with Colour. 
So there are a myriad of combinations.

Here we present a simple spreadsheet of my own results to date. Each print of the model takes ~~ 35 mins so some time is needed to properly test each combination.
My own focus today is on Supports for Polymaker's CoPA Nylon.  Because Polymaker themselves do not divulge what supports work best with it. And yet CoPA with CoPA supports do not separate easily, and leave a shite surface on the model.
I also tested PLA with PETG supports, and PETG with PLA supports, plus Generic TPU 98+ with various supports including PLA.
Your focus will be on whatever model material you need to work for your current project. At least this test takes only 35 mins and 7 Grams of material for each combination.  A worthy investment if quality is one of your goals.

My overall goal here is to shed some light on this obscure area of 3D FDM printing. Towards better education of 3D printer users.