I'm going to say Champs has the most instability simply due to sponsorship parent company... moving from Foot Locker to Eastbay to Champs has not helped the brand of the race.
NXN cancelling for 2020 and especially 2021 hurt their brand and allowed Garmin (now New Balance) RunningLane to enter the scene in a big, big way.
RunningLane will continue because it's a true open championship. No politics, no at-large bids, no regional qualifying, just show up and race mano a mano.
Thankfully I've been blessed to run them all and enjoyed them all, but it would be nice to have one post-season race. Right now, real-time, NXN has all the hype... but the media cycle is short-lived and Champs will have the final word and buzz like it always does because it is last and all the media entities need content and NXN fades.