Why is my new replacement battery always dropping from ~80% to ~25%?

There is a "known issue" that often the Apple software to report battery condition and charge tends to"fixate" on 96% as the maximum charge... therefore it's good that you are using several different apps, but it appears you are obsessing about your battery state.

Each time you complete a charge cycle, it diminishes battery capacity slightly, but you can put notebook battery through many charge cycles before they will only hold 80% of original battery capacity. Using the battery until it is mostly discharged is wise... but completely discharging the battery is not, unless your Macbook is the one with a removable battery.

So to recap it's not good procedure to never take your laptop off mains power, nor is it good to completely drain your battery, except as a means to rectify having it on mains power for days on end.

OEM batteries are warrantied for a year against defects, and with AppleCare can be extended to three years from the date of your notebook purchase with the AppleCare Protection Plan. However, the AppleCare Protection Plan for notebook computers does not cover batteries that have stopped working or are exhibiting diminished capacity except when it is the result of a manufacturing defect.

I truly hope this helps.