Tree Style Tabs, Sidebery, or similar are must-haves. I do try to clean up my tabs regularly, but I almost always have more open that can conveniently be displayed in a horizontal tab bar.

Vertical screen real estate is at a higher premium in general on desktop, anyway. No point in keeping my browser at the full width of my screen when most sites adamantly refuse to use the space anyway (case in point: Lemmy).

Yeah I hopped back over from Edge when the manifest v3 stuff came out, and the two main things I miss are proper profile management and vertical tabs - I've been using https://codeberg.org/ranmaru22/firefox-vertical-tabs to get around it currently, but having a native implementation to both issues will be a massive (and recently rare) Firefox W.