There are no system requirements for these individually, as they are Apps you add to a Jira system.
If you need something to say "we might need a bigger server if we install these", then take a look at the hardware requirements for Jira, and depending on how much you plan to do with the Apps, simply add some users to the number you are specifying your Jira for. I'd probably add a 1-2% for Automation and another 5-10% for Portfolio assuming a lot of your users are going to use them both.
For example, if you expect to have 100 users, then read the hardware requirements table as though you have about 110.
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