I tried using Zen as I moved away from Arc, it really tries to be Arc but had a ton of issues at the time(6 months ago). Ranging from performance, different parts of UI crashing or behaving weirdly, to typos in English translations all over Settings. I settled on Brave for now because I won't give up uBlock Origin but I also didn't enjoy using Firefox long term for some reason. I honestly loved Arc, but I won't use product they won't work on anymore.
Brave is a good option too. I use brave for websites that are too junk to work in firefox. I have never used arc. I was coming from librewolf/floorp with sidebery. I really like the layout in zen, it hasnt shown the performance issues i sometimes saw in stock firefox and the vertical tab bar is good enough yo replace sidebery for me. Tge only annoyance ia how it sometomes weirdly display extensions in the truncated interface. Otger than that i am pretty happy.
