To add multiple ssh keys to your system, you need to edit config file ~/.ssh/config and put lines like below, this will also help store password for your ssh in keychain and use agent forwarding so you can use your keys on virtual machines like vagrant

This problem with access permissions has become common in latest versions of Mac OS, you need to give permissions to apps (executables) so they can do/use stuff on your disk/computer. Most of the times you will get a prompt for asking/checking this but sometimes this will quietly fail.

So file synching is a pain int he ass on MacOS so I made some tests with "wrk" tool to see what is what and how much request per second can each config handle. I started with install.php on D8 site as it is more about file and less about database and caching. Tool was used with this config (30s of requests) 

For complex application, provisioning your box with the initial “vagrant up” command can take a long time. Fortunately, it’s not necessary to do this for every member of your team, on every computer that will be used for development. You can use the following command to create a filename.box file, which is the already provisioned box.