What's the best way to create an opportunity with associated custom objects ?

Hi,

When we create an opportunity, we want to be able to create and attach custom objects to it. For our usecase, an opportunity has multiple devices : escalators, doors, elevators... attached to it that will later be priced independently under the same opportunity.

We would like the user to just enter the number of devices, like : 

And have those 10 records created automatically and attached to the opportunity. But after the opportunity is created, it should not be possible to edit those numbers, only editing the records directly.

We were thinking about creating a custom Flow for this, but maybe there's a better option ?

Thanks !