Best solution for performance - to extract 400 over fields with varchar (300) for one single BI Data set

I have this requirement to extract about 450 fields with most of it's fields length with varchar(300) from multiple tables for one single BI report. For better performance, I tried to create one single table to store all the required fields. However, it exceed the SQL server max row size and table was created with errors such as cannot insert or update the table since it exceeded max row size limit. As such, It seems like we have to split the tables. Then I am afraid for the extract performance. During extract time, we also need to apply data level security. Do you have any idea for better design to get better performance?