Both of these features are designed to prolong battery life and both halt the battery charging when it reaches X% (default is 80%). However the Thinkpad feature lets you prevent charging altogether within a range. ie, you can a percentage that it must be below in order to start charging. This is key to actually helping preserve your battery.
I'm probably a typical laptop user where I might have it unplugged during breakfast so I can do emails while eating. This may take me 10-15 % of my battery capacity before I move to my office, where I plug it into my USB-C Dock.
At this point the Thinkpad will do nothing, because it is not below my threshold (I have it set to 35%).
The Thinkbook will automatically start to charge back up to 80%. Every single day, it charges the battery back up. This greatly increases the number of charge/discharge cycles which is what wears out your battery!
My Thinkpad can go 4 to 5 days before needing to recharge and still has a great battery life even though it's over 3 years old.
Lenovo, PLEASE update the Thinkbook Vantage Battery Conservation to use the same logic as the Thinkpad. Your customers will lover you for it!
Thanks!