Quad Remesher 2.0 will feature Face Sets as guides and possibly an improved algorithm, but it might take another 5 to 6 months, according to Maxime, the developer.
I don’t know if there’s a Decimate modifier alternative, but I did some comparative tests between ZBrush Decimation Master and Blender’s Decimate modifier a while ago, and found them to be pretty comparable. The only differences I can remember is that Decimation Master allows you to decimate with an adjustable degree of detail to preserve vertex paint (Polypaint), and it allows you to decimate based on masked areas.