I am in family practice. I do have to take call one night a week (I have Thursdays, 6pm to 6am Friday) and every 6th weekend, but I was offered jobs that did not involve call as well. Call is not a big deal, frankly. It mostly involves telling people to take 2 tylenol, "put some ice on it," or go to the ED; b/c I can't see "it" over the phone and I personally will not call in scripts or give advice about a condition I cannot see and have not evaluated. That is just my personal policy; some other providers do call in antibiotics, etc. I do not, will not, ever. It is simply a liability issue, IMO. The patients get upset, but I have a colleague who got his pants sued off for calling in a refill Rx while on w/e call and the patient had a simple adverse reaction anyone could have had. It wasn't as though they were allergic or anything, but he got totally screwed because he had never actually examined or even met the patient. That isn't going to be me.
Our practice patients know they are supposed to request refills 5 days ahead of time, so if they don't do it, they are SOL and it is not my problem if they fail to plan, and I'm certainly not calling in their refills on their word. I don't even have access to their e-charts at home. Besides, it's just reinforcing bad behavior. If it is emergent, they need to go to the emergency room, if it isn't, they need to call the office and make an appointment to be seen. If it is in between, they need to go to urgent care. I don't need to be wide awake for any of that. The only real issues are critical labs, etc. Those I actually have to do something about, but the lab calls at 9:00am Saturday morning, not in the middle of the night.
A few weeks ago I got a 2am Sat night /Sun morning call from some drunk idiot who fell down and wanted to know if I thought his wrist was broken. My spouse said I was quite rude, but how could I not be? How the ever loving @#$! could I possibly know if his wrist was broken? Why on earth would he have me awakened to ask me that? He was drunk, and a jerk, and yes, I probably was rude as told him to either sleep it off, put some ice on it, go to the ED, or all of the above, but don't call me back, lol. I never heard how his story turned out, but the important thing was, he didn't bother me again! Most calls I get nothing more than simple straight forward questions that are entirely reasonable: worried new Moms, new hospital discharges with an issue, an occasional adverse reaction. I don't get a lot of calls and the few I do get are generally legitimate. Every once in a while you get one that makes you wonder about the future of the human race, but by and large, call is not a big deal at all and not a reason to worry about NP practice. My patients give me a lot more trouble during office hours than after.
As for flexibility in general, I think that depends on the job/practice. I have enormous flexibility. I can come and go whenever I please and make my own hours, so long as I meet my .8 obligation. I change my hours all the time, depending on what my family is up to. I have different hours during the school year than in the summer, for instance. I don't take a lunch so I can arrive a little late and leave early. I work some half days, or take a whole day off to chaperone school trips. I just try not to bump a lot of patients, and I would never do that at the last minute. Other than that, anything goes.