Smart Mirror - how to find the right balance between monitor and mirror

[Linx]

Hey, there are multiple mirror sizes available and I am unsure about whether the size of the monitor and mirror will be “in sync”. I am thinking of buying a 12" x 18" mirror. Advice for what size monitor to get? (Going for a budget mirror)

shorturl.at/ntxIT -> It’s an amazon Link trust me on it

Also, anyone has any examples of what sizes they have used for both the mirror and the monitor?