If you want to fly fast, you can use resilience's twerk function to use fly to fly up to speeds of 6.9. Other clients like H&E have better kill aura, but no option for adjustable flight speed.
It's decent but in my opinion some of the other clients kill aura are better. Also, while the twerk + flight combination is being used you cannot use projectiles (Throw able bottles, enderpearls, bows, experience potions)
I recommend flare. The fly is easily tweakable to a good speed by playing around with the fly speed, speed multiplyer and sneak speed. Also it has a way better killaura than resilience and the Iridium H&E remake, although you can't hit through walls which can do with Iridium H&E
H&E does have adjustable flight speed. H%E has a better killaura than all the clients listed above, you can move and fly fast and can hit through anything. H&E is the way to go.
H&E is bad tbh I use x_iGold_x's client it has fly speed to 5 and can kill people with p2 within gapple
I'm confused here, you say it's called "x_iGold_x" then you say you wont tell me what it is called. If it's a public client it's not that much of a secret.
I would personally recomend H&E. It's pretty much a remake of Iridium, which was the best (by far) client out there.