For a very long time I've used the Martin Logan curved panels which are quite dependent on positioning so have possibly become a little over attentive to those requirements. I've had 5 pairs of these over the years and never had any of them in the forward facing mode. On the other hand, when using conventional speakers I don't think I used any but a slight toe-in. With these Serie Reference monitors, that's where I started, with zero toeing.
I'm trying not to become fixated on the equilateral triangle positioning of speakers relative to the listener but there are enough discussions supporting that setup theory that I think it's worth considering as, at least, a starting point. Right now the speakers are positioned 12 feet apart with my listening spot 16 feet from them in a room about 18 feet wide and 25 feet long. I can make some minor adjustments to the furnishings to put the speakers 14 feet apart with the listening position 15 feet from them. With the speakers this far apart I'm thinking that some toe in would be called for and I'll begin experimenting. I'm still impressed with these 20 year old speakers and am sure they'll be in my home permanently.