Sounds like you are probably half way there with your thinking.
On the road you sit in the same position for much longer and I find being a bit more stretched out with more of your weight taken through the arms than backside is a good start point.
Try adding about 20mm to your stem length and if you want something that gives you options to move your hands about but that is not a drop bar than look at the Fleegle Pro from On One. Have done many miles on my Road Rat with a trimmed version of teh standard Fleegle and find them much more comfortable than a straight bar. If you have shifters/brake levers that have smooth clamps you can also ride with your palms over them and I often do that along the straights (you can still operate trigger shifters and brake levers with outside digits).
I swap whish way up or down the rise of the stem is depending on the type of riding. If off road a fair bit I’ll flip it to positive rise but most of teh time it’s got neg rise for on the road. This only really works with shallow stem rises though.
If you are single speed I guess you still want a wide bar and a standard un cut Fleegle might be the ticket. I miss the width when I’ve tried SS with my cut down versions on the MTB last winter.
I also have some midge flared drop bars and dia-compe 287v levers attached to a Carver SS but they aren’t wide enough for hilly SS off road I’ve decided. Ok for road and tame bridleway.
Hope that helps a bit.
