New pc config. Bitlocker and Microsoft personal/business account while using Office 365 business

I'm configuring a new laptop for a client. Since W10 had the "find device" option if you configure with a Microsoft personal account I thought I'd use a Microsoft personal account that he has.The only reason he has a personal Microsoft account is because of the way Windows "herds" users into thinking they must use or create a Microsoft account. while setting up a new computer that is connected to the internet. He previously setup another laptop himself.

To complicate matters this user has an office 365 business subscription so that they can install desktop versions of Office to their computers.

I'm wondering if I'll be ok using a personal account to log into the computer and installing the desktop apps from his 365 subscription.

Also, does anyone know how well the find my device feature work? Personally, I can't see how it will help if someone steals the machine. Even if they turn it on, they can't login to connect to wifi, and there is no ethernet port. So how would the laptop even be able to connect to determine and report it's location?

Another concern that I have is in regards to bitlocker. What happens if he changes his password from the web, or other pc? Will bitlocker let him in on this pc?