(And if you aren’t familiar yet with Chrome tab groups, you can get an in-depth look at how they work on the desktop front here. The setup is essentially the same on Android: In that Chrome tab overview area, you can just drag and drop different tabs on top of each other to group ’em. Then, once you have a group, you can tap it to view all the tabs within it, rename it, or assign it a custom color.)
One last note that isn’t obvious from this settings section: With or without that auto-opening option, you can also manually find and open tab groups from other devices within the Chrome Android browser.
Just go back to that tab overview screen — once more, by tapping the outlined number on Chrome’s address bar or swiping downward on that area of the screen — then tap the four-square icon directly next to the tab number count at the top of the screen.