The simple answer to that question is a resounding no.
I have tried my Legion Slim 8 with and without them to see firstly if there's any difference in battery runtime in Quiet Mode and second if they impact on benchmark scores or not because of interfering with new AI performance management in the AMD Ryzen 7840HS and the Lenovo LA2-Q and LA1 AI chips on the system board.
There's no benefit in Quiet Mode for battery runtime and with regards benchmarks, the answer is the old power plans do indeed impact on scores. Not massively but even so, it's consistently 400 points down in Cinebench running the Performance Plan from W10 Legion Power Plans set compared to standard Balanced Plan mode in Windows 11.
Why? The BIOS triggers automatic overclocking when the notebook is under high load and the Windows 11 balanced power plan is selected (nothing to do with the options in Vantage). So installing and using the legacy power plans effectively disabled that as Legion Balanced Power Plan does not get detected as 'balanced' by the BIOS.