Might just be a personal gripe of mine, but I found that sourcing nvm in my zshrc made my shell startup times significantly slower, which also affected adding new windows with tmux. Not sure if it's a problem for you, but here are some things that made it better for me (Now im lazy loading nvm with fish though, but yeah i used some of these at some pont)

mise I've heard good things, it's like a global package manager and a replacement for asdf which was kind of ish popular, will do node and other things, haven't tried it out yet
volta Haven't used, you define the node version in the package.json and likewise, pretty popular too, article comparing it and mise https://ricostacruz.com/posts/mise-vs-volta#:~:text=Volta%20doesn't%20add%20any,to%20run%20in%20my%20machine.
fnm or n FNM is a rust package, it's syntax is a little weird so you have to do like fnm install -- --lts, n is a node package, so you can just you system npm. Startup times for these are wayyy faster than nvm and i think they're the best drop in replacements.

your tmux config is fire. please upload thanks. 🧍‍♂️