I don't personally feel much difference online versus OTB, but some claim it impacts them a lot.
There are many reasons this might be. One common one is the evidence that confirms some people can "see" the board better (tactics, hanging pieces and similar) with 3D vs 2D or vice-versa. It comes down to basic conditioning of the brain; if you practice a ton of chess only on a 3D board, then it might be hard to adapt to a 2D screen for some; similarly, players who play almost solely online might have trouble adapting to a 3D perspective.
Luckily, you can "re-wire" your brain to see both by adapting through simply practice. Whichever one you are worse with, just do that for a bit more than you used to do. Some people might adjust in a week and some might adjust within 10 minutes; everyone is different, but if you play chess online and OTB like I do, then you are less likely to dramatically suffer adapting as you are already accustomed to both.
As for quality of opponent, it really depends on what level you are playing at. Higher rated chess players are more likely to vary less. An online GM is probably similar to an OTB GM in ability (partly because all titled players on chess.com have proven their identity to get their respective titles online, but really only OTB titles "exist" - if you are a GM in real life, then just reveal this to chess.com and they'll give you the "GM" title online).
Even if not titled though, a 2000+ rated chess player online is likely to be within a few hundred points of their OTB rating. Chess is the same game online or in-person.
However, chess players under 1500 chess.com rating may vary more compared to OTB due to factors like lack of experience (nervousness OTB etc.) or more opponents online not playing as seriously which inflates your rating; remember that pretty much ANYONE can join chess.com and the vast majority are recreational players to play for fun or as a hobby.
Conversely, an OTB tournament setting has everyone more serious about chess because they entered said tournament and there are typically several costs (financially as well as time).
So I do not have a great deal of experience OTB, but I play my friends who are not very good at chess, they do not study or know any openings. I usually crush them and end up in some strange positions where I end up with a mate without realizing it. Meaning I do not see the mate before I make the last move.
On the contrary, I notice I miss a lot of mates when I play online chess despite having some familiarity with the board positions (as I normally play the same openings and my opponents have similar responses). I am only about 1150 rated in Rapid, and rarely play anything else.
My main questions really is, Does anybody else notice a difference in their own play in OTB vs online with chess.com? Do you think it is because of the quality of the opponent that there is a difference, or does it potentially have something to do with seeing the board in person vs on a computer screen. I'm interested in seeing what differences you may see in your own playing styles.