I bought my 7 in November and it's at 87% battery health. I already have the "featured" installed as I'm at 11.2.1; however, that feature is not affecting me as much as I have an Apple Battery case that keeps full the internal battery at power.
Double check to see what your CPU speed is currently. Use Antutu or CPUdasher.
Some noticed slow downs on the i7 on 11.2.1 even when over 90% battery health.
And Plugging in to an outlet or external battery pack will not bring bring the CPU back up to original speed once the slow down is implemented.