I think this is a question of whether you want to scale horizontally (adding more nodes) or vertically (adding more resource) in the future.

When you reach out the maximum resource of what your DBMS can handle, if you stick with independent database, it sort of allows you to go from either horizontally or vertically, but if you stick with one database, you will be limited to vertical scaling.

You should analysis the cost between adding new hardware vs adding more resource to find out which one suits you the most.

I used to have similar form building system, not built using Laravel tho, I actually did one database with prefixing tables to store clients' data Tho, the data was not like yours which has 10,000 rows in a table, but it did serve me well. :D

Well it's basic model where I have other companies to rent my application service. Then I add them as clients. I can have up to 50-100 of them maybe, so it means I would have 100 databases with 15 tables.

If I use 1 database, just with other table prefix, I would have single database with 1500 tables.

What is better performance wise? What use more resources etc ? any idea?

You don't have to have 1 database for 1 client. You could use a master database for managing indexes and equally distributed your tables across multiple databases. (That was what I did for a project for managing astronomy data in college, it has a huge data set. )

EDIT: Sorry I am not sure about the performance of using Laravel. I was using Java and JDBC for doing that astronomy project.