Just switched from logi options to Steer Mouse myself.
You can map the buttons and add chords. The only thing it might lack is being able to use mouse movement as a trigger (eg hold the back button and move left to change spaces). Still looking for it
SteerMouse really is an amazing focused piece of software. I’ve had it for a decade now and it’s up there with Alfred as a must have. It used to have issues with BTT and Karabiner but it’s been very smooth since it switched to a full app recently.
I switched about a year ago. After about two days of trying it, I was throwing money at them. It's sooooo much better than Logitech's enormous blob, and actually looks/acts/feels like a Mac app. It was totally worth the small price.
You can map the buttons and add chords. The only thing it might lack is being able to use mouse movement as a trigger (eg hold the back button and move left to change spaces). Still looking for it
https://plentycom.jp/en/steermouse/