Where I work I use a mix of these -UV tools https://hqdetails.com/shop/uvtools -Tex tools http://www.scriptspot.com/3ds-max/scripts/textools-toolbox-for-the-texture-artist -An internally developed uv tool UV tools is pretty good but it is 20$. At home I just use maya its default UV tools are great. =)
http://help.autodesk.com/view/3DSMAX/2022/ENU/?guid=GUID-9E98AEAC-F06F-4FAD-9091-DCD30AC9BB26 Straighten Selection tool only works with rectilinear layouts. There are a bunch of tools in there though to help out with straightening. You can also try Spline Mapping…