I don’t think anyone said as fast as possible. You asked about NVMe.
Get yourself a single hard drive. It seems like it’s all you want to spend. It won’t work well, but at least you know the bandwidth won’t be wasted!
And yes, writing raw data from sensor is going to be different than playing back raw footage from disk in resolve. It’s a completely different process.
A three drive raid-0 hard disk array would be the least amount of kit I’d recommend with reservations. A five drive raid5 wound be better. And driving a Ferrari to get the groceries is purely sublime. You should try it!