RS 700. Do I really need a subsciption for it to work?

Netgear routers do not require any subscription to function.  There are some features which can be enabled only by subscription, such as Bitdefender Armor and Smart Parental Controls.

The also do not require use of the Nighthawk smartphone app.

You can take a Netgear WiFi router "out of the box", plug it in, and (for most ISPs**), begin using it with the WiFi credentials printed on the label.

** If the ISP requires customers to supply a user name and password, those credentials have to be entered into the router before it can connect to the ISP.