Custom connection rate limit per ip list or per http header Irule

You may see my irule as a base reference:

https://community.f5.com/t5/technical-forum/f5-irule-table-command-rate-limit-or-block-http-requests-in-two/m-p/294027

For calculating how much memory it will take there is no way for that that I know of but even when I used the table command I didn't have any issues withe F5 memory and usually the F5 irules impact the CPU the most so there is a calculator for that:

https://community.f5.com/t5/crowdsrc/irules-runtime-calculator-spreadsheet-generator/ta-p/285478