I found it funny and I din't know that when you set game details to HQ it uses constantly only 1stperson model versions of the weapon. How to prevent this effect while i need to use different models for TPP and FPP? Lowering details is not a solution nor I wouldn't like to quit using different models.

I've searched INI files but most of the lines are mystical to me so if someone would like to give me a tip I would be grateful.

I don't think my aging machine can run the game at "high quality," so my only experience with this would be the way the engine handles third person models, first person statics, and alternate textures. We may not be talking about the same thing here. In vanilla, I think, the weapons are configured to use a given model, but the configured model is used for third person perspective. This is because the weapons are set to use separate models/textures in the form of (what FO3Edit calls them, at least) first person statics. I think most of the vanilla weapons have their statics set to use the same model as in third person, but use alternate (possibly higher quality) textures. I don't think many of the unique weapons have first person statics configured.

So, you could whip up a patch of your own to have weapons use whatever models and/or textures you want in first person or third person (I think there is an option for world models as well.) Most mods don't use separate models or textures, and many that even do use statics will actually just duplicate the configuration for the third person model and alternate textures. In the absence of a first person static configured for a weapon, it looks like it just falls back to using what otherwise would be the "third person model." I'm not sure if there is an INI tweak you can set to control this sort of thing, but, assuming we are talking about the same thing, you can definitely do this in FO3Edit or the GECK.

The problem is that I am using either GECK and FO3edit, that is not a point. I prepared different models for 1st person slot and 3rd person, and swapped them with vanilla ones but the game uses only 1st peson slot if you set high details and never see 3rd person model this way. The same goes about low quality - then u can see only 3rd person model. Models are used separately somere between low and high settings. If there is no tweak around it in INI (or so) then the thing is rather lost as hardcoded.

Edit: Never mind, no clue.