I see others have beaten me to it with more helpful and probably more constructive comments.
I actually live in Darlington, have worked on Teesside and have family near Osmotherly and in Northallerton, and (to me) the A19 is just not a nice road to drive. It’s fast, but with a lot of local access points so much more joining/leaving/crossing than you’d expect for a road that busy and fast.
It’s also the main spine up and down which people drive to and from lots of “dormitory” type towns and villages to work on Teesside; round Wynyard, and up to North Tyneside and Newcastle.
If you live east of the A19 and are commuting to Darlo, you either have to cross it and then go overland round Northallerton, which is getting much busier and is also subject to a bit of a chokehold with two train crossings at either “end”; go up and then through Yarm, which is like swimming through treacle at rush hours, or go up to the flyover and then west along the A66, which is busy and thankless. On paper it looks like a 40 min drive to Darlington, but I’d guess a daily commute at anything like normal working hours would be way in excess. There are some lovely places round there (including Stokesley) but they’re not great to drive to work or to catch train from Darlington.
Northallerton is nice but IMO just that. It’s also growing an awful lot and there’s not really any walks of interest without a decent drive first. There are London trains but not anywhere near as many as Darlington and I think (don’t quote me) they’re reducing in number.
Hurworth just outside Darlington is good for schools and very pretty and community minded. Heighington similar.
Richmond and surround villages may also be worth a look, but my money would still be on Barney tbh.
Good luck!