Yeah, the current gen cars are (very) roughly equivalent to F3 cars in terms of overall performance. Hopefully the Gen3 cars can push closer to F2 (they're still going to be miles off F1)
F2 is about as performant as IndyCar, except on high speed ovals where IndyCar is better than anything else (F1 is not designed for that.) I believe that's possible to build low cost cars as performant as a F1 but it's not in the interest of FIA to sanction that kind of series because F1 must be the fastest one by definition. The "pinnacle of motorsport."
To back my statement: if you look at the race times for the last 20-25 years F1 cars didn't get any faster at completing a race. They got faster at completing a qualifying lap so we could say that current cars are built to run hot laps and have to enter into a slow mode to run a race. BTW that cost billions of cumulative engineering efforts. If somebody tells Dallara to build 20 copies of a Ferrari F1 car from 2004 (Ferrari won 15 out of 18 races that year) you'll have a v10 series much faster than any IndyCar or F2, only slightly slower than current F1 and it will cost a fraction because of the reasons for IndyCar costs a fraction of F1.
Monaco is special in a way that power does not matter there that much and even downforce is not so important, so comparing different cars over that track does not make much sense.
Just because it's not a typical circuit doesn't mean the comparison is useless. To your point though, Monaco is the best case scenario for Formula E when being compared to Formula 1.
https://formularegionaleubyalpine.com/corsa/monaco-2021/
(This is really Formula 3 https://en.wikipedia.org/wiki/2021_Formula_Regional_European... )