Dear Joost,
I appreciate a lot for your effort and feedback. My approach was to share only the actual challenge I am facing without the context so in case it is something really obvious it is easy to answer and I save time for everyone. 
But it seems it is far more complex than I thought.
In our organisation we implement many projects and activities where we are handling thousands of applications who then becomes hundreds of participants.
Our problem is that we do not have one comprehensive database where we can see ALL the people in one place who we managed to reach out offline and online and then handle their applications separately, connected to the specific project and activity they are applying to.
My idea was to do a three steps registration-application-confirmation system, where we can see in one table all the people who are interested, then we can handle their applications activity by activity. 1 project has 1 coordinator but it can have several activities.
What I established so far:
Project coordinator registers a project and add activities to that project where they will receive registrations and applications. Each activity has a separate application form about motivation, experience, several activitiy specific questions, documents to attach etc.
I created a template with a standard application form, what the coordinators can tailor made, create a form and they copy-paste the link of the application form to the specific activity.
I created a “link generator” table where they just select the activity they want to receive applications and I divided the application process to two steps: 1. Registration, 2. Application to specific activity.
The generated link is a generic registration form what we ask from every single person who applies (name, email address, country of residence) information we always need with a hidden field which tells which activity they are interested in.
This generic form has a hidden pre-filled column with the activity code so we understand from which activity proposal they got the link. They fill in the basic information, the hidden form tells us the actual activity they are interested in and in this way when they submit the registration form I created an automation which sends an automatic email to them with a personalized link to the specific activity.
This is the form what the project coordinator created and tailor made to the specific activity. Motivation, experience, etc. and after submission this lands in a separate table while we have in the registration table each people interested, and in the activity specific table each person applied to a specific activity.
I understand there is the option to simple create table views for each specific activity, however it would not work because in this case for each activity each question will be there and with time it will be overwhelming to go through each time and hide the ones not needed and add the new ones. That table would gradually grow and we do not need motivation and experience in the table where we want to see all interested people, because that would be too heavy.
We are talking about 30-100.000 rows.
So that is why I chose to use a connector which connects the table with all people to the specific activity. At this point the only information I would show in the overall table is the “status” of the person if they applied, selected, rejected which is an activity specific information.
So what I am wondering basically how would it be possible to feedback to the overall table information when the activity specific tables will be definitely duplicates?
I am trying to see if the relation column keeps the setting if I create a template for the activity specific applications. So then the project coordinator just use the template, create a new form, copy the link to the form and then customize the questions whatever is the need of that specific activity.
Does this help a little or confuses more? 