I think 300-350 is about the minimum that I'd want in a vehicle. Especially considering the normal "buffer" you want to keep, and the effects of weather/speed.
Here is a copy paste of a post of mine in another thread. I did a ~840 mile road trip (~1700 mile round trip, each leg of 840 miles completed in a single day) this summer (like every other summer). I was curious and I kept track of our distance between stops, and their length (as I'm considering a full EV). Maybe this will be interesting for others.
-----------Copy/Pasta----------
I just did a ~840 mile road trip on Sunday, and have been curious about this, so I was actually counting, and timing our stops.
Keep in mind this is a single day, one way trip (ie, just the return leg of a road trip to visit family). Also, keep in mind the below is all averaging about 75-80mph (we drove WA to UT, and this leg was from UT to WA. Most of Idaho and northern UT are 80mph speed limits, with people going way faster than tha)t.
Also, our vehicle has a tiny fuel tank (11gal, because its a PHEV), and I have a mountain bike on the back on a rack. All these things together (high speeds, tiny tank, bad aero because of bike). And not once was the range the main limiting factor. Although it was very close on the first stop.
Stop 1: 258 miles, over3 hours of drive time, and a ~15-20 min stop (I forgot to time this one exactly). There were lines at the fuel pumps (every pump was full, and there were at least 5-6 vehicles towing, with the line out almost to the street).
This had the highest avg speed of the trip.
This was the closest to an actual fuel range limit. We had under 1/8 tank left, the fuel light was on, and it showed an estimated 9 miles of range remaining when we pulled up to the pump. But the kids had been clamoring for a bathroom break for 20 miles before then, and I was pushing the range a bit, wanting to get to a better place to stop. Ended up putting 9.998 gal into the 11 gal tank.
Also, FWIW, I still had ~90% battery charge here, so if we were really in a bad spot, I could have turned off the gas engine, and had ~20-30 miles more range to get us to another pump if something went wrong getting fuel somehow. So while I was pushing it, I wasn't totally crazy

.
Stop 2: 207 miles. 11 minute stop, timed with a stopwatch.
limited by kids bladders. Still had like 1/4 tank or so.
Stop 3: 221 miles, 9 minute stop, also actually timed from moment we drove in, to moment we were pulling out of the gas station.
Same as above, about the kid bladder limit.
Keep in mind we're averaging ~80mph or so on these. And even at those speeds, thats 2hrs 45min of driving, which isn't bad.
That... was it. The last leg home fit under the kids bladder timer limit, and we made it home with like half a tank of gas.
~830 miles with 3 stops, and ~35min of stoppage time.
We didn't stop for anything but what you see above. We have all our food in the car (wayyy easier with kids, who are often hungry RIGHT NOW, and have a hard time waiting for a fast food place, we just get a bunch of good food/snacks in a cooler, and we graze as we go, because eliminating food stops chops a bunch of time off the trip (its easy to spend ~30min or more at a fast food place).
I didn't think to get the data on the way there, at least not the specific mileage/times. But I do know that we stopped 5 times on the way there, and at least one of the stops had a HUGE line at the bathroom (when we were only an hour from home... of course), and we were likely there at least 20-30minutes.
I'd say that leg of the trip we had a combined total of at least ~1hr - 1hr 15min of stoppage time, and we were limited entirely by bladders, rather than fuel.
Sorry, huge rambling post.
TLDR: I think for non-towing use cases, ~350 miles of range is totally fine for families with kids, even at high speeds
For towing, the range changes considerably. Also, 350 miles of range could not be enough for those with super bladders, diapers (children or adult), or really low average speeds (350 miles on a ~50mph highway is about an hr more drive time than at ~85mph)