I would like to ask about URL link of the client area

Hello,
Sorry,I'm a beginner.
I need to change a URL link of the client area but I have a questions;
1.How to change it?
The present URL is mydomain.com/whmcs that automatic since my web developer installed it.
Example : I need change to mydomain.com/support or change to subdomain is support.mydomain.com
2.If I change it, Does it reflects anything or not?
Example : shopping cart link , order form link
3.I should set up configuration and integration already or not?
Because I work it 80%completely.

Please suggest me.

Regards,
Thananit