Amazing visualisation, an excellent tool.

Are there other sites that can suggest how much of an issue it is, and how much flight plan tweaking could improve this.

Remember kids a 1° C rise in temperature can mean 7% more water vapour in the air, and with water vapour being a greenhouse gas itself this can cause heating and holding yet more water.

The site itself has more information. https://contrails.org/

I guess the map is posted today due to this recent video (worth a watch): https://youtu.be/QoOVqQ5sa08?si=sGK9Q9tUoFOW1QZg