how can I change the resolution from 1080p to 720p or like smaller?
preferably right from the start
Using Command Line Interface,
cp /etc/X11/xinit/xinitrc ~/.xinitrc
edit the file (I used vim) and edit the line that allows you to set resolution.
Search with "xrandr" on this forum, you'll find what you need.
Important : you need to go through SSH to make it works.