How is life as a PhD research scientist/staff scientist in academia?
In my experience there are two types of staff scientists.

The first are people who go out and get their own grants. Basically, if an institution thinks you have a legitimate shot at acquiring funding, they will give you access to their grants office to allow you to submit a grant to cover your salary and lab space. If you are good enough to bring in your own funding, life is good. You can live/work wherever you want and more or less name your own salary (of course you need to bring in the grants to cover the salary). As your salary is tied to your grant(s), there is a lot of stress associated with going down this road. A six month funding gap can be disastrous.

The second are people who work on the grant of someone else. This puts you at the same risks of having a funding gap, but know you are not responsible for getting the money, but someone else it. It requires a good working relationship with the PI as they have to be able to justify why paying more for a staff scientist is needed. It terms of flexibility/security, if the PI loses funding, leaves, or retires, getting another job can be really difficult and you should not expect to really have choices in where you will end up. Often grant funding, especially NIH funding, needs to be planned 18+ months out. People just don't have unallocated chunks of funding large enough to cover a staff scientist.