[bestest]

ok. can someone explain to me. I've been using ctrl+r for god knows how long and it solves all my shell completion needs.

is inshellisense for average users like me or more advanced users?

[fostware]

If you're more used to ctrl+r, you could try hiSHtory (https://github.com/ddworken/hishtory)

[serial_dev]

I use zsh plugin, autosuggests, and ctrl r, too.

Ctrl r is okay and it is a very convenient if you already typed the command.

Inshellisense seems to help with knowing what subcommands, flags and file paths are available, and it even provides a small docs helper for the flags and commands.

If you didn't try these tools, I'd encourage you take a look, it helped me a lot, especially when I work with tools whose commands I don't know by heart or used a while ago.