Hello,
First of all, thank you for your purchase.
If you have a good server (VPS or managed), your site speed will not be affected by the installed plugins. If you have a shared hosting, you will need to experiment with it, to see how many plugins can it handle, as shared hostings usually offer lower performance and can be affected by multiple plugins getting installed and activated on it.
You can also check with hosting provider’s support, to ask details about their recommendations, which are specific to your current server environment.
Regards, Szabi – CodeRevolution.