Upgrade your battery
Some background. I recently got a Legion Go Z1E secondhand on marketplace. I wanted to get a Steam Deck OLED so I can give my Steam Deck LCD to my wife after she tried it and fell in love with being able to play her favorite games handheld away from our desks. Unfortunately they've been almost impossible to get from Valve and they're way overpriced on the secondhand market. I found a listing for a Legion Go 1TB for only $400 since he just upgraded to a Legion Go 2 and decided that would have to be enough. I threw bazzite on it because Windows was frustrating and I've honestly been incredibly happy with the performance ever since. The only problem besides the cooler sounding like a jet engine under load was the atrocious battery life. Less than an hour in some AAA games despite my best efforts to improve battery life.
So I did some research and saw that it's really common and easy to upgrade the battery. Without hesitation I ordered an 81wh battery and I replaced it in less than 30 minutes. I did have to remove the battery frame thing and used electric tape for cable management but overall it was an easy and painless experience. That was a week ago and the battery life has been great ever since! I get almost 4 hours in FFXIV Dawntrail! With how cheap and easy it is I consider this a must have upgrade for legion go owners!