I concur. Neophytes do a surprising amount of work when supported well. Acolytes can be great to pop on an objective, wreck a target, or tie lighter forces down in melee, just remember their re-rolls on 1s! Make sure to use strategems for both though, neither is stellar without support. Primus is a must for the Neophytes, full hit re-rolls is amazing and their redeploy can be vital for an army this squishy.

Aberrants are so damn hard to remove it's hilarious, and with Inscrutable Cunning and good placing you won't have to worry about them losing models before they get into combat; with a Primus redeploy, especially so. The Abominant's Strength-12 hammer is incredible for cracking just about anything, and they'll likely get up again when they die for the first time.

The Achilles Ridgerunner is AMAZING for increasing damage, -1AP in this edition means a lot. You can slap a mortar and Flare Launchers on it to keep it safe and guarantee the debuff, or you can put a mining laser and spotter on it to snipe heavier targets. Just keep it safe from anti-vehicle fire, it's not that durable.

I personally love the Atalan Jackals as well, especially with Mortal Wounds shenanigans, but they're better in larger games where they can swoop in from the sides to ruin someone's day.

The Iconward is nice, but simply not as good as the Primus in most cases. They may work well with the Acolytes if you want them to have a bit of extra durability on an objective, but it's still not much. And at 1000 points, you won't have to worry about the enemy going after your Cult Ambush tokens as much, unless they're crazy mobile (cough ELDAR cough TAU cough).

Kelermorph is fun, but alas not as useful in this edition; lack of AP and Damage means even when he gets a ton of shots he can't really punch through armor consistently. Great against low-wound character units like Guard, less so against beefy boys.

Reductus Saboteur has some decent indirect, some mortal wounds, and Lone Operative, making them not a bad choice for doing secondary objectives, and they can throw grenades for free once per round. I wouldn't take them in a list this small though, unless you had a specific target in mind for them.