Do you think that PROJEQTOR can support this huge volume of projects/incidents ?

Is there a problem of performance? slow execution or not ?

Connection can be a bit long if users are affected to many (hundreds) projects.
It is due to project-based access rights that are calculated during connection

If i have a hundred of projects by user and i make a default filter for each user

Do you think that calculation of each project can be executed normaly or taking bit long time ?

The default filter will not help.
If is the number of affected projects that will have effect on performance.
100 projects is not blocking but may lead to connection up to 30s.
Then running projeqtor should be no issue.