There seems to be an assumption that there is such a thing as a multi CPL. There isn't. Some people choose to do a combined CPL and MEP course (28 hours) and do the CPL test on a twin, which means you don't do PFLs but do do asymmetric work instead. At the end you still have just a CPL whether it is done on a single or twin. The only requirement is for a number of hours on a complex single and to take the test on a complex, so you cannot do the CPL on a C150. It is worth checking the various schools to see how much time is actually spent on a complex aircraft. Some only provide for the minimum, which I think is 5 hours, whereas others do almost all the flying on a complex. Some schools only offer the CPL on a basic single and a twin, and try and sell it as a better route. The reality is that they probably can't afford to run a twin and a complex single!
The IR on the other hand is either a single engine rating or twin rating depending on what you do the test on.
The twin rating on its own is 6 hours and one exam and can be added to a PPL. I am about to go this route.