There is no
single correct answer on bevel angle.
The bevel angle on a spindle/detail gouge partially determines how aggressive the cut is.
With a low, 25 degree bevel angle, you get more of a paring cut. This can be great for softer woods and fine detail work but does dull more quickly.
With a higher, 40 degree bevel angle, you get more of a scoop like an SRG or bowl gouge. This can be good for harder woods, making the edge last longer but does not provide a fine enough point for some detail work.
this is one of my detail gouges, ground between 35-40
Attachment 516464