I wanted to make a CPU and then somehow measure its efficiency/ speed. Logisim is a little buggy, and I don't think it allows you to do any sort of testing/ measurement. Does a tool like this exist?
For a complex project such as this, you would be better to use an HDL like Verilog or VHDL and a simulator.
There are open source Verilog tools available like Icarus. Also since all the major FPGA vendors have a free version of their dev tools, you could just download and use these.