If I have a SharePoint Farm with 2 web frontend servers. Am I required to load Nintex Workflow and Nintex Forms on both web servers or can I get a working install if I only load each product on 1 (the same one) of the 2 servers?
this is depending on the licensing type you prefer. In general all products need to be licensed on all web front end servers.
If you choose subscription model, which is licensed per complex workflow, the amount of web frontends doesn't matter. You just license the farm for the amount of workflows/forms you want to start with and can then add all products to all your web front ends. This is the most flexible licensing method as it allows you to run your workflow in Office 365 and the Nintex Workflow Cloud too.
However there is a classic licensing model. With classic licensing you will need to license all products you need on all web front ends. If you want to use Workflows and Forms on 2 web front ends you will need to purchase 2 Workflow licenses and 2 Forms licenses. As classis licensing is per server you don't need to care about how many workflows you want to run but prices per license are much higher and you won't have the option to use Office 365 and Nintex Workflow Cloud.
I suggest you get in touch with a Nintex partner. They can help you find out what licensing option is best for you.
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