Hello,
The dev team has tests with more than 5000 rows in a single table, a lof of them with WordFragments and the result is very fast. We recommend you to check if your server is configured correctly or it can be optimized, maybe if you are generating too many objects it's running out of memory (or using swap memory) or any other problem (buffer limits, not using an opcode...). Using Xdebug could be helpful to get the source of the problem.
Anyway, about your question: using a Premium license, DOCXCustomizer can change content styles on-the-fly, so you could generate the table using plain strings and then use DOCXCustomizer to change styles using DOCXPath queries. We recommend you to check the documentation and the included samples.
Regards.