Level 1 charging is C/5 (5-hour) and Level 2 charging is about 0.46C (2 hours 10 minutes). Surprisingly, I read a study that said that the battery life was similar for Level 1 vs. Level 2 charging. With Tesla superchargers, the battery life substantially degrades, as you are up to about 2C charging. Lithium-metal solid-state batteries, which will first be available in less than three years, will solve the fast-charging problem and will even do 4C with minimal degradation in battery life: https://www.quantumscape.com/resources/blog/white-paper-a-deep-dive-into-quantumscapes-fast-charging-performance/
Not a surprise for people who have had their Prime for several years and been on L2 the whole time and still have the same battery capacity as a new Prime. L2 currents are nothing compared to what happens when you drive it.
Charge-Mode delivers twice the punch as L2. You can see that in this video, on the aftermarket app (right). It averages 7.2 kW.
I wouldn't say nothing. When you are driving, you are experiencing about 0.6C (100-minute discharge) for the discharge leg of the cycle if you average 20 mph. Level 2 charging is 0.46C (130 minutes) for the charge leg of the cycle; so, they are comparable. If you continuously experienced the peak discharge rates during hard acceleration or peak regenerative-braking charge rates during hard braking, which could be as high as about 7C and 4C, respectively, for the Prius Prime I believe, the battery wouldn't last for more than about a dozen cycles.
That means it is not a good idea to use it unless you occasionally need it. The Prius Prime battery isn't capable of having a long life with 1C (1-hour) charging.
Except that once the battery reaches a certain temperature going down a long, steep grade, it switches from regenerating to engine braking. I've had that happen. So ... if the Toyota engineers were dumb, it wouldn't last long, but they aren't dumb. I'm not sure that can be said for the human interface engineers, but that's another topic.