There actually is not a training for making your whozhit move any faster.
The efficiency training cuts the production time for making parts by a half second, capping at .5 second for production of parts. It is intentional that his energy depleted faster after upgrading, because he is working faster as a result. Youll need to keep a closer eye on his health and energy or else he'll collapse or jump in the uhoh hole.
Both energy trainings (fitness and workplace) allow your whozhit to raise their maximum energy capacity, which allows them work for longer before needing to rest which is essential for later game working (and preventing death) after you have leveled up the quality training and youre in need of more parts to make whutzits that sell for more money.
These are definitely mechanics that aren't really gonna get shown off except for people that REALLY stick with the game for a few runs, which probably isnt the best idea for a game jam, but my goal was to make a game that people could continually get better at and I think the scaling has been pretty dialed in. I hope that helps clear up any confusions!
My highscore is around 32 days now haha.