I use VSCode + SSH remote for this and works great. The only nitpick I have is needing to manually reconnect when I suspend my laptop and ssh connection breaks. It's a separate session though, which doesn't matter to me but may be a deal breaker for you.
I use Tailscale for a personal VPN so the beefy workstation is always securely available from my laptop, even when across the pond).
There's no input delay in VSCode (editor, ui) because the UI is local. Delay in saving/reading/sesrching in files is not noticable for me.
(edit to explain: VSCode is still running locally, but it also installs the server-side (headless) component on the remote machine. That way editing files is local/fast, but stuff like running the code, search/replace/etc also works fadt because it's handled by the serverside).
Terminal (incl vscode terminal) feels slightly sluggish, and it's noticable if the server is in another country and uncomfortable if across the pond.
The input delays are very dependent on where the server is and what it is doing. If the server is idle and close by (ping wise) delay is virtually indistinguishable from local VSCode. If I'm connecting to the server via a VPN in a different country while stressing all the cores with some background compiling or number crunching work, input delay gets quite noticeable.
I multiplex my ssh connections so the workflow is just ssh sgain, then reload VSCode window. If Mosh could multiplex these (and paper over the connection problems) that'd be great but after a cursory look, it doesn't look like it's possible.
It's a minor thing tho.
In general, I quite like Mosh! If I routinely had to work on faraway servers I'd use mosh just for its smart local echo.
I use Tailscale for a personal VPN so the beefy workstation is always securely available from my laptop, even when across the pond).