We are going through something similar and it seems LANDESK has not really been able to provide any guidance on what the limits are. It's going to be somewhat hardware dependent as well as how many instances of your forms are being opened at one time. In our environment we do around 1200 incidents and requests per day, some of our request forms have 15-20 calculations on them per form, we run one app server and 4 web servers, to date we have not seen any performance issues in anything we have done but are about to add many more forms and processes which is where I have the same question as you.
If you don't get any guidance I'd say the best thing to do is benchmark performance in your current system, including stats from task manager on your app server. Make the changes and re-benchmark. I think the biggest factor is going to be how many people are using the form concurrently, as the more users trying to use it will result in more load on the server.