Tmux is more customisable, but a lot messier out the box. It's much older so has picked up a little cruft along the way.
Zellij is newer so has the benefit of being a clearer implementation. But it's designed as an "out the bix" experience, not one you can customise to your hearts content.
Edit: if you did want to try out zellij, I should point out there's a "no install, try in shell" option on their website's main page which is a super quick way to get a taste!
I have definitely felt that. Customization wasn't necessarily straightforward - just required some time spent reading the docs.
I appreciate the heads up about the "no install, try in shell" option. I will make sure to take a look!
Last I tried it the bind issue and performance were sort of blockers for me, but it looks like both of those are moving forward.
I don’t know what it is about how my brain works, but I have absolutely no memory for keybinds (and envy those that do), so I love that it just lays them out in the UI.
Only customisation I make is to turn off the borders.
Would love if built a similar, visually guided, experience for nvim.
Definitely would recommend checking out Helix. My brain is similar in that keybindings often don't stick - Helix has a grammar leading to a bit more of a visual interface (you select things first, and then edit, so you can see how things go as you carry out multi-cursor edits etc), but also, it'll show pop-up menus for shortcuts.
In normal mode for instance, "g" is "goto", pressing g also displays a little window that shows the different options and their keys. It's easy to ignore when you know what your doing, and super helpful when you can't remember something!
Should say that it's really similar to the tmux/zellij distinction, in that, helix works nicely out the box, but is a lot more opinionated, there's LSP support for pretty much all languages you'll use, but no plugin eco-system, so if you have a really customised, or AI based workflow for instance, your kinda stuck.