I spent about a decade working for one of the NNSA labs. I think they're a good place to work, but it's a very different work environment than startup culture. Most of what I'm seeing in the discussion is pretty accurate. I'll add a few things in case they're deal breakers.
It's likely that you'll either be required to or pressured into obtaining a security clearance. Have a look at Standard Form 86 (SF86) and see if you're fine with these kinds of questions. Depending on how comfortable you are with this line of questioning, do note there will be more digging especially if you've lived abroad, had prior drug use, had prior legal issues, or a variety of other items that pique their interest. Failure to obtain a clearance is grounds for termination in most circumstances.
A clearance comes with certain responsibilities. You will have to report certain kinds of travel even if on vacation. You will have to report certain kinds of contacts even if not work related. You may not be allowed to freely publish even non-technical documents or books without prior approval depending on the level of clearance. There is a way to accommodate the lab in a way where you can mostly live your life freely. Most of this is just paperwork. However, you do give up some of your autonomy.
There is a proprietary innovation form they will push you to sign that will assign to them all innovations even on your personal time without company resources. Likely, this is not valid in California. Not sure if this is currently negotiable. They were pretty insistent in the past.
Pay for a starting Ph.D. was a little over $100k about 10 years ago. It capped out for most people at around the $130-140k region after 10 years of experience. Likely a bit different now, but not tremendously so.
While it depends on the group, internal politics heavily favors pedigree and degree level. Meaning, you are treated better if you have a Ph.D. even if it's not really necessary for your position. I'm not sure I would consider a job there with less than a masters. Practically, this means you're more likely to be the PI with a higher degree. More likely to be selected for promotion. More likely to be able to move to management if that's of interest. More likely to obtain internal research funding. To be sure, I don't agree with this, but it's a reality of the culture.
Things like time card fraud are taken very seriously. Meaning, if you work extra hours, you will be compensated for it either in terms of flex time or pay with overtime. Management doesn't like to pay overtime, so this means that you'll likely be out on time most of the time.
It's a professional workplace where people come to work and then leave. As such, no alcohol on the facility, no gaming tables, or sleep cubicles or cutesy architecture. It's not that people are completely serious the entire time, but they are professionals and there is a pretty strict separation between what's considered business activity and personal activity.
The research projects are great. There's easier access to grant money than in academics and it provides the opportunity to work in areas that are not necessarily commercially viable, but have broader impact. Getting access to the money either means being good at proposal writing, and having the right pedigree, or making friends with someone who is and likes to farm out work to you. When I say money here, you're not going to make anything more on the grant. It means being able to buy out your time to work on this particular project.
That's already probably too much, so I'll stop here. In short, I think they're a great place to work if you can fit into the culture with them. They tend to play by the book professionally and tend to hold by their agreements with you. However, there is a lot of paperwork and you will necessarily give up some of your personal autonomy.