Supporting HTTPS and HTTP on same CRM On-premise?

Hi,

We are currently running CRM 365 version 8.2.2 On-premise, We would like to allow one of our partners to access the Web API REST service in order to retrieve/update some data in CRM.

Our CRM is currently using HTTP and is only available to our internal users.

We do not really want to install the full IFD as we don’t want our CRM users to access CRM from outside.
It looks like we must install HTTPS and then allow our partner to go through the firewall. Only traffic from their IP address will be allowed.

1) Is it possible to install HTTPS in addition to HTTP on our current CRM? I see in the deployment manager that we can only choose one or the other.

2) if not, what is the impact (performance wise) of using HTTPS instead of HTTP for our current users?

Thanks

Christian  Betrisey