some skins make your fire disappear and you will start lagging ( for my self i have a skin pack from cs1.6 but its golden )
so i recommend not to install them to your game they will lag you and make your fire not stable
It is a side effect of having too many skins, yes. But having few skins does not affect the performance unless they are badly made skins. It all depends also on one's machine.
*Edit
before suggesting anything, you should actually check the quality.
http://cs.gamebanana.com/skins/134698M4a1 skin is so bad that, I don't know, you don't really want it. Same as with the rest, even the rating is a giveaway.
Also, why you are showing off skins? Did you make them or smth?