I am interested in finding out what someone has to take into account when he wants to make a new palette and how those aspects are matched with a specific equipment.
Since there are a lot of rubbers and blades available on the market, we will not talk about a specific brand;
instead we will consider only their general characteristics: stiff/ flexible blades, soft/ hard rubbers etc.
Probably a lot of people will tell you to test different setups until you find one that suits your playing style but in practice this approach will not work for a lot of people because they do not have that budget and even if they have it they need to start with something.
And yes, a lot of people will tell you that it is a matter of personal preference but since you have not tested many equipment you do not have that experience to compare them so there is no "personal preference" available for you.
Last but not least, you are still developing your skills/ technique so some of your strokes are not properly executed so instead of changing the palette you need to learn more table tennis.

So, let's assume that you are a coach for example who has tested a lot of setups and you have seen the person for whom you are going to make a setup how he is playing table tennis.
What aspects are you going to take into account to make a setup for such a person?

The guy has just started to learn table tennis so a flexible blade will be suitable for him.
The guy has a strong backhand so a hard rubber will be suitable for his backhand.
The guy plays close to the table so a soft rubber will be suitable for his forehand.
If the guy attacks with the backhand, you will not put long pips on the backhand side.
When to use a stiff/flexible blade?
When to pair a stiff/flexible blade with hard/soft rubbers?
As a guy who is learning table tennis you do not need a carbon blade.

In other words, I am trying to find out what's behind the "It depends." answer given to the question "What is the right setup for me?"
Probably there are some general guidelines to follow and aspects that you are looking for when you make a setup.

Do not take the examples above as rules on how to setup a blade; they just aim to better explain what I mean with this post.

Best regards