Disruptive is probably the most useful one. Everything else is nice but feels like not so much benefit for the investment.
Mythic Disruptive is only adding half your tier, so it only starts to get good at higher tiers. I guess even a +1 or +2 is nice when talking about Concentration checks, but it feels... well, not very Mythic.
I'd probably pursue the whole Step Up line, though it's sort of diminishing returns again. Following Step is slightly bizarre in that you can move up to 10ft, but only to get adjacent to a foe 5ft away. Still, it gives you a bit more flexibility, and doesn't rob you of your 5ft step next turn, so it's good for positioning. It's a fairly fringe benefit for a feat, though. Step Up and Strike is pretty good since it essentially means that 5ft steps provoke - but only once per turn, since you need to spend your immediate action - plus the benefits of Step Up... it's quite a lot of investment by this point for just 5ft steps, though.
Mythic Step Up actually might not be awful because it expands that to all movement, which prevents Acrobatics and Withdraw, but it still has a lot of limitations. Also as written it's kind of weird - you take the immediate action as they move away from you, which presumably means they are only 5ft away at that point - then you attack, but then they carry on moving. Thus, the extra movement doesn't help at all? The intent seems to be for you to follow them all the way and then attack, but you'd better hope then that you have a greater speed than them. Perhaps a DM will let you make an attack at the last possible moment? Anyway, it doesn't help with the immediate actions.