I love Vivaldi due to vertical tab bar But I use Palemoon (Firefox fork with XUL) with Tab Kit for vertical tabs too

I think Vivaldi (based on Chromium) is great for one time browsing (open -> close) But I got a bunch of sites I visit daily so I got them opened in Palemoon and open them when I need With another extension you can also unload tabs (manaual or auto, config it as you like) in Palemoon like Vivaldi (called hibernate in V)