Hi @mfsi-akshay, thanks for the kind words!
The delay you're experiencing in insert mode is expected as Vim has to wait after you hit space to see if you're going to then hit
jk. In general I recommend not having any leader mappings in insert mode. Instead, the most common thing I've see is to map
kj directly (without
<leader> before them). You'll see the same delay with the first character of those pairs you type, but once you hit any other key Vim will respond.
kj are rare enough sequences that you're likely safe to use them.
In the past I used NERDtree to provide a project file layout sidebar. It works very well, and if you're really missing it then by all means give NERDtree a shot. In my case, I've found a combination of vim-vinegar (minimal directory explorer functionality) and CtrlP / fzf (fuzzy file finders) do much faster and more intuitive.
Most of all, I'd recommend trying out a few different things and seeing what works for you.