We have been working remotely in our company for more than 4 years.

We work in asynchronous mode, that means that everyone works whenever they want, we do not do daily stand-ups, we do not use Slack, and we rarely communicate through video conference.

Due to the current pandemic, people have been forced to work remotely in a synchronous mode. That means having a permanent video conference and permanent chat witch in my opinion is a torture.

Our tools are:
Basecamp as the main communication hub.
Screen for pair programming
Whereby for video conferencing

That’s the ideal option and I always insist on async work on all my interviews. I am after all paid to deliver code and business value. In 19 years of career I can’t remember more than 10 company meetings that legitimately helped me in my work.

That’s an oddly general question but IMO nothing much changes compared to what you’d use on a company machine. Here’s what I do:

• I use my personal machines for work. That’s what I bought them for: to have excellent equipment at home. I almost don’t game nowadays so if I don’t code, I almost wouldn’t need computers anyway.
• I backup my work code repositories (and DB dumps if any) aggressively – several times per hour – on a local self-hosted ZFS NAS server. I also put encrypted copies on a cheap VPS.
• I use asdf to manage different versions of software – not only Erlang and Elixir but also PHP, Python, Ruby, even databases like PostgreSQL and MySQL and many others. Then I put a .tool-versions file in each project’s directory so the languages and DBs are automatically switched to the proper version when I cd into the directory. I found that setup to be extremely valuable because it gives you a a local environment that’s adequately close to the real production environment. (Of course that approach is technically inferior to using Docker or NixOS for complete isolation but I found that with enough diligence I can skip those otherwise excellent tools for a leaner setup that works fine 99% of the time.)
• I use fzf and skim combined with ripgrep and ripgrep-all for extremely fast lookups of code snippets inside files, or to look for a particular file.

TL;DR: invest in per-project environment isolation. Backup often. Learn your tools intimately. Such knowledge will pay you off many times over.

I work 9-5 mainly because it aligns with my colleagues and I work on a side project in the evenings.