Ours is pretty simple. You have a "cash" fund for bidding on free agents, but the salary cap is determined by how long you sign them for. In our league, we don't pay an annual salary. We pretend that we pay it all up front. That removes the problem of dropping a player that you signed to a long-term contract.
To explain the cap, it's also pretty simple. We simply add the total length of every contract on the team regardless of the age of the contract. In other words, a four-year contract counts four years toward the cap every year. So a roster with 10 1-year contract, 10 2-year contracts, and 5 3-year contracts would have a cap figure of 45 years.
There are other nuances, but that's the general idea.
Hope this helps with what you were looking for!