Ideally it would be nice to “link” the brush size to the current zoom amount. Then if you zoom in/out, the brush could scale correspondingly and paint the same size relative to the object. Maybe this isn’t practical. It’s really significant when painting with a texture, not so much for lines etc.
I think I've heard both Kent in sculpting and JL texture painting, saying that you shouldn't spend too much time in orthographic, for the same reason you say, it can distort things, because it flattens the depth. I guess in perspective if you have a wide lens it can also distort things. I would say though that being in orthographic while sculpting is worst than in texture painting. The brush size would be cool if it adapted to the zoom, there might be an addon, try searching in the Blender Market. But in the end, I guess being mindful of your stroke and zoom just becomes second nature the more you texture paint. Perhaps other software's have tools that adjust the brush size to your zoom. I might google that.
In Sculpt mode there is an option to set the Radius Unit to Scene for consistent brush sizes, but for whatever reason that wasn't added to Texture Paint mode. I do agree it would be useful!
Orthographic view can maybe help reduce distortion sometimes when painting, depending on the angle, but I don't think it makes a difference when it comes to the zoom level and brush size. I would agree with Omar and Kent that orthographic view is generally not good for sculpting, but I don't see a problem with painting details that way if you find it helpful.