You need not fret. If it’s a 4K player it WILL play regular DVDs and Blu-ray discs :-)
That makes the mental math easier for me: if a 4K will handle both formats, then that’s something I want.
I don’t know if 4K is worthwhile for you. I can barely tell the difference between 4K and 1080p on my 65-inch screen. On a thirty-something screen, it may be gilding the lily.
Sony doesn’t have the reputation they used to, but they still make a good product.
It would stay away from Samsung. Their support is awful.