1. Everyone has to use the same IDE 2. Everyone needs to stop doing local dev.
That first one seems like a massive hurdle. It may be one. Vim users tend to look down their nose at IDE's. IDE folks think vim users spend more time playing in vim than working. And we all want to forget about people who use VS code. (I say this having 2 open vim sessions, 2 IDE's running and used VS code today to build some firm ware).
There really is one choice at this moment. Pick intellij (or one of their branded products) and code with me. Dont fuck around with VS code. VIM is NOT an option. You need everyone using the same tools so that you can work in files together (think dual cursors), or in the same tree concurrently. You also need to let someone take the wheel of your machine (think kvm/vnc) or you theirs and work effectively. Someones vimrc file is going to be disaster for you. VS code is just too incomplete and too easy to experiment with odd ui and plugins. If you have a die hard vim user then just put vim in your IDE... and lern how to toggle back and forth if loves vim that much.
This gives you a fair bit of the tooling your going to need. I cant stress enough that all of you are likely going to need desks, and matched monitors... You cant have one of you in 4k and one of you in 1080. Its going to be a nightmare when you need to share screens. And your going to want to share screens.
The other side of this is moving to remote dev. In an ideal world you all live in the same city, still have an office (or access to some rack space) where you could put a server and run prox mox on it. Everyone would get a VM (a whole, real VM) and then run containers/what ever they wanted on that. Why does same city/office matter. Because the spead of light is a bitch... if it takes a 1/3 of a second for the one team member across an ocean they are going to be really unhappy. If your all spread AND every one has good internet AND can poke the holes needed then set up a bunch of mini pcs's at everyone house... You can also just rent servers from someone like OVH (flat rate, unmetered bandwitdh) again pay attention to latency.
Why "remote dev"? 1. easy to backup / restore (even more so with a tool like prox mox) 2. You can now take risks, having back ups, not risking your dev instance do that dumb thing. If it goes badly just turn on the backup. 3. You can do this to someone elses dev env! If your having a problem or trying to recreate a complext bug, or chase an issue through a deep stack you can all trouble shoot on the same instance. Hell you can break that, restore and be back up and running in zero time flat.... At no poit is your personal work computer, with your mail/slack/logins ever at risk of getting knocked out.
The whole goal is to end up with a LOT of parity and a lot of access. You all managed to agree on a programing language, a data base etc... the rest of this is just furthering that standardization. It is going to feel weird, it is going to be rough the first two weeks but if you spend a lot of time with open voice chat and accessing and looking and making an effort to be involved in each others work your going to find you get a LOT of productivity gains.
It is a tough level of collaboration to maintain your going to spend the first month forcing it for an hour a day for 3 days a week. Your going to spend a bit of time over indulging (where you end up spectating too much) ... when you all get comfortable with it the exchanges just turn into "hey can you look at" for 5 mins here and 10 there with some weekly catch ups, group code reviews and really paring for the gnarly changes.