Is backcountry camping legal and/or available near these pools, or or is the 3 Forks CG the best option for an overnight stay in the area? (Thanks to any locals answering!)

People camp there often. Park rangers hike to the springs often. Mainly towards the evening hours.

I've seen people set up hammocks and camp. Also if you drive up the canyon a little more there's free camping.

There is a turn out right before the trail hard called dry canyon and it's free to camp.

Thank you, Nicole and M Morris!