Welcome to the site !!
Don't have experience with it , but it does look to be available .... What I would personally do is contact Ohlins and ask them specifics on whether it will help with the issues you are having
https://www.ohlinsusa.com/parts/honda/c ... rally/2018
As far as comparing it to the KTM ... The 250L was not really meant to be a competitor with the 690 , that is a beefy bike that has really good suspension and is very capable off road ... The L unfortunately , was more designed for the "casual" rider that might occasionally ride on a fire road , the 450L is actually more off road capable than the 250L by a long shot , even though the suspension is similar and not really adjustable , the 450L is just more stout and can handle more , I have read on one of the MX forums where 1 guy rode a 450L on a MX track and did well on it , he even had pictures of him jumping it , he actually rode it to a MX track , ripped around on the track , and rode home , lights , signals and all .... the 250L is not so capable ..... I am sure you can do things to improve it , but it would be a stretch to think it would be as suitable and I would not expect it to be comparable to the 690 in any way ....
I am a Honda guy thru and thru ... but there is no way I would expect the 250L to be anything more than a "fun" bike and practical for anything other than basic street and fire road riding ..... and is definitely not meant to be pushed hard off road ...... and there is no way I would compare it to a 690 KTM ... it's not even in the same category ............... I would sooner put a street legal kit on a 250X or 450X as they are both very capable and adjustable for off road , and not that hard to make street legal ....
I actually ride my 450X on a GP type MX track with no issues , it is very capable of pushing it , I was hitting 20ft jumps with it , I ride it on the same track I ride my 450R on , and I don't putt around tracks and I am 60 ....the X yes , and is easily modified for a heavier guy , a L ... not so much ..at least for anything other than as I mentioned ... casual riding ...