No, we never make changes to the core files of Magento 2. Marketplace Multi-Vendor Module for Magento2 is coded on the base of Magento 2 Application Programming.
Magento 2 Marketplace module is scalable which means it will not affect your existing store performance and will support all your standard Magento 2 cache handlers.
There is no limit at vendor and product level and any number of vendors & products can be added to the store.
Please do contact us for any further queries or requirements. You can also check our Magento 2 Extensions for additional features.