In fallout lore, (not in game) can a person hold and use a firearm and a power fist or ballistic fist etc... at the same time ?

 And also what was the real purpose of the power fists in the pre war time. Some of them seem to be used to industrial work (industrial hand), others to self defense (ballistic fist) and some to conter power armor (paladin toaster), whats your opinion overhaul.

We haven't got anything in lore, but here's my thoughts on the different types.

Fallout 1 & 2 - They are basically a glove with some servos, so I would say "Winter equipment grip" so most pistols would be out.

Fallout 1 "Mega Power First" - similar to above, but has green glowing bits, along with the spiked knuckles, so again I would say "Winter equipment grip" but a bit more difficult.

Fallout Tactics - same as above but less glowing bits, so I would say the same.

Fallout Tactics' "Impact gloves" - Heavy gloves with wrist support and long spikes on the front of the knuckles, should be safe to use rifles and pistols.

Fallout Brotherhood of Steel - Electrified one with an on-off switch, but looks like a thick leather glove, so should be easier to use with all guns and pistols.

"Van Buren" - Icon looks like a medieval armoured gauntlet, so should be a bit thick, but doable with pistols and rifles.

Fallout 3 & NV - We've seen that you can still manoeuvrer your fingers, but have a large pad (the trigger mechanism for the pneumatic system) over the upper part of the fingers, so I would say doable, but be very careful.

Fallout NV's "Beartrap Fist" - Forget it.

Fallout 4 - Forget it.

@"McKaby"  "Fallout NV's "Beartrap Fist" - Forget it" - I laughted more than i should with that one...
Also dindnt know Van Buren had power fists, really wished I could play it. 
 But yeah I think the same they probably are a complementar weapons for close quarters.

Aye, I see them as more of a "lets go over the top" deal for melee than a knife, with the added bonus of not being able to be knocked out of the hand.

But the "firing mechanism" in all of them are a little off putting if there isn't a safe toggle switch.

im sure there is a toggle switch, but i see them as a way as intimidation against raiders or a counter against robots that u lure towards u and surprise them, or even power armored enemies.

Rly ? A toogle switch ? Nice ! F@ck I want a ballistic fist and know....(and dont take this the other way....  or Lord Caesar will spank my ass)

It depends on the power fist. The type that works like a glove like the displacer and the ballistic fist can let you hold a small firearm and can let your finger fit the trigger guard.

The industrial ones like the newer power fists requires your fingers to operate the power fist which would hinder your from grabbing a firearm with the same hand.

This question also makes me wonder why the game lets players wearing power armor wield firearms. How does that huge finger fit the trigger guard?

In the current state of the games, you can't. If ever BGS thinks of implementing that system, they have to revamp the equipment slots in a way that you could equip a power fist at your left hand and a pistol at your right. I also believe that with a mechanic such as that, dual wielding is more than possible now. Of course this is all wishful thinking. Imagine crippling an enemy with a 45/70 govt to the knee then finishing it off with a punch to the face resulting in a headsplosion.

Well, there is a mod, that add implant, like servos on your arm, but it's not a power fist. Just look and +some stats. Mostly cosmetic.

@"ahyuser001" I was wondering the same, maybe power armor units manly use heavy guns, or melee weapons like kinetic hammers.

@"njmanga097" That would be extremly satisfying...

@Vizsla That was what I was thinking. Power Armor, at least in my mind, was used as mobile armor that uses heavy ordinance like missile launchers, 50 cal machine guns, gatling guns, energy weapons, etc.

There is no way that those suits could use small arms.

@"ahyuser001" Like a one man mobile tank/shock trooper right ?! They could had a little flavor by making the use of power armor have a disanvatge of like -20% to small guns etc... But thats just me complicating things in my mind.

@Vizsla To me it is a matter of immersion. You could just restrict small arms entirely but buff up resistances towards kinetic damage when wearing a suit of power armor.

It looks silly to look at a someone wearing power armor holding an AR rifle for example when the finger is tightly fitted in the trigger guard. And how about the trigger itself won't it get broken when you shove a huge metal finger into the trigger guard