Question | can run firefox with imacro on the vps?

Yes. Since imacro appears to be a firefox addon it should run on any platform supported by firefox. If you create a new Ubuntu 14.04 or Ubuntu 16.04 droplet and on the create page, check the “user-data” box and paste in the following script your droplet will be configured with an XFCE desktop environment and the x2go service which I think is a better option than VNC (it runs over ssh so it’s encrypted by default and supports ssh-key authentication). You can download a client for Windows, Mac or Linux here.

#!/bin/sh
export DEBIAN_FRONTEND=noninteractive;
apt-get update;
apt-get -y install software-properties-common xubuntu-desktop firefox;
add-apt-repository -y ppa:x2go/stable;
apt-get update;
apt-get -y install x2goserver x2goserver-xsession;