I was brought up in Netley Abbey, and worked in Southampton for 20 years. I have now retired, to Wales...
If you want to refer to Regents Park, don't refer to Millbrook, which is not the same, most of Millbrook is an appalling shithole, and dangerous. I used to work for the council, on social housing maintenance, and was threatened or attacked there more often than anywhere, even in St Mary's which was my usual patch. I dislike Southampton intensely, but I have probably experienced the worst of it (drugs, prostitution, violence, death), and not seen much of the best. Thornhill is not brilliant, but is much better than it used to be. I am not convinced of the realism of working in Southampton and living in Ventnor. Make careful study of transport costs and timings, and prepare for huge transport expense, that is a very expensive bit of water to cross, but not quite as bad as the much shorter crossing of Portsmouth Harbour from Gosport (I worked there, too!).
Netley (NOT to be confused with Netley Marsh, which is somewhere else entirely) is OK I suppose, a large village, which is primarily a dormitory area for Southampton. It has a railway station, but check the service frequency, and it has access to countryside.
I'm a bit jaded about the area, having lived in it or near to it for 60+ years, and now live in very rural Powys. If you want to ask specifics, feel free to ask, I certainly won't give you a romantic notion of it, but my view is probably a bit too jaded to be what most people would experience.
I would say that the area is generally fine, but pick where to actually live, very carefully. There are some lovely bits around there, so look carefully and you'll find them.