What positions should I put X-factors on

I'm trying to figure out whats good and whats not

I always like universal coverage on my Dbs or Safeties.  If you get them activated they make passing super tough.  Then I usually put one on one of my edge rushers.  I have fear monger on Peppers right now since throw under pressure really impacts QBs.  On offense, Freight train is a must on a HB.  QB is the most important position so put one there, but it depends on play style.  Some like EA, some like Bazooka, others find Omaha helpful.  Then I usually put one on my best WR.  I have Double Me on Megatron right now.  Here is the tier list for abilites

https://www.mut.gg/abilities/

On defense, I usually mix x-factors between my corners or safeties. I'll typically use universal coverage on my DBs. I like the concept of fearmonger and unstoppable force, but I find it too difficult to consistently activate these in H2H.

• Universal coverage - The most physical coverage defenders prevent catches from happening even when their target has hands on the ball. When they enter the zone, they are nearly guaranteed knockouts.
• Fearmonger - Some pass rushers intimidate quarterbacks with their sheer presence. When they enter the zone; they can apply significant pressure on quarterbacks even while engaged with blockers.
• Unstoppable force - Elite pass rushers are a mix of strength, speed, and tenacity. When they enter the zone, this ability increases their win rate and block shed speed against one-on-one pass blocks.

On offense, your abilities are typically scheme dependent. If you're run heavy, then I would make sure your RB has an x-factor. I prefer freight train since I typically use a heavier RB (think Bettis or Henry), but if I went with a shiftier or receiving back, I'd use first one free. If your pass heavy, then you can ignore your RB and focus your x-factors on your QB, WR, or TE. I'll typically put an Omaha on my QB, since having the ability to see your opponents coverage pre-snap is incredibly powerful. I typically put Double me on my top 2 pass catchers (doesn't matter if it's a WR or TE). Sometimes Double me can be hit or miss, but when it works, it forces my opponent to double cover a pass catcher or risk giving up an aggressive catch. If they double the receiver with either their user or a CPU defender, it should open up the field for your other pass catchers. If you run a balanced offense, then I would go with x-factors on my QB, RB, and then your best pass catcher.

• Freight train - Freight Trains are relentless runners who refuse to go down on first contact. When they enter the zone; this ability increases their chance to break the next tackle.
• First one free - Some players thrive on making defenders look silly. When they enter the zone; this ability increases their fake out rate on the next juke; spin or hurdle.
• Omaha - Elite quarterbacks are molded by endless hours of film study. When they enter the zone, they have full vision of the seconday's defensive coverage before the snap.
• Double me - Aggressive receivers overpower defenders and attack the football. When they enter the zone, this ability increases their success rate on aggressive catches against single coverage.