is chess.com rating roughly equal to an elo/fide rating?

Yes, chess.com elo is supposed to resemble a fide elo.  It uses elo just like fide.  I don't know what your question exactly means though in the description.

The chess.com uses Glicko elo, which apparently is just elo with an added way to calculate how accurate the elo is based on how many games you've played.

Well I mean would a 1400 rated player here also be about 1400 fide rating or uscf rating or not so much because chess.com is its own thing?

A chess.com player would likely be a bit lower elo than 1400 fide.  Playing otb can be very different and time controls might also be different.  Of course you can always find whatever time control you want but most, at least in my experience, are 15 min +.  Most chess.com players play faster games, to be honest.

https://www.chess.com/blog/smarterchess/chess-rating-comparison-2016

This comparison was pretty well done.

Honestly, there's no good way of knowing what FIDE/USCF rating you would have because it's a completely different pool of players.

Well I think chess.com's blitz players pool are tougher, the other two ratings there comes close to my rating.

i think that blitz games are not the same sport that long games it s like saying that sprint is not the same sport than marathon just like long games are not the same sport than correspondence games

i knew a fide master and a champion on correspondence games who was not so great only 1600 elo over the board

and i think that online blitz games are not the same sport than over the board blitz games it s like saying that apartment bike is not the same sport than bike on the road

i know that it s a little bit cliché but i think that you can t compare things that are not the same

Who as 3000 and more in fide elo ?!

And in the middle (1600-1800) the chess.com elo looks be harder.

I don't think it's completely true, but in some point it can serve as approximately true

Smarterchess updated his study last year:

https://www.chess.com/forum/view/general/can-chess-com-ratings-represent-otb

Yes, they're both numbers.

Yes it is

I guess

Chess.com ratings seem to be around 200 to 300 points higher than what one's FIDE rating would be.

So 2000 on chess.com would likely be around 1700-1800 FIDE.

Though, it varies from player to player.

the graph it is very easy to analyze...at low level in chess.com you can find users with medium level playing very random without compromise....they can disconect for whatever reason...but in high levels are less people with good level that play radomly.