Advice for Management Software

[Jaime Suez]

Hi everyone! I'm new on Rails and coming from PHP world (Symfony)

I want to do a management application. Most of things that I need are CRUD, list, search... so  an admin interface is ok for what I need. I have seen RailsAdmin and has great functionality.

But my question is about performance, because my application will have many concurrent users. So, will using an admin interface will drop down the performance (memory and speed)? 

It would be better to make things by hand or with the admin?

Thanks!