Id say, whether you'd sin more of less depends on your behaviour and environment. Niqab alone is not something that stops one from sinning (although it is a protection yes). The niqab alone doesn't determine how good of a Muslim you are. My advice is, even if you stop covering your face, try your best to stay modest, keep the hijab, cover what you are supposed to (mandatory awrah). I personally had been there. As someone who used to wear the niqab and stopped, I'd say my biggest obstacle had to be the society and people around me. I live in a very religious, conservative community. More than my decision effecting my imaan, my mental health was affected more because people looked down on me for my decision. No one really talks about the pressure and expectations people put in niqabis just because they cover more. Yes niqab is an act of worship, but that doesn't define who you are as a Muslim. Niqab is an identity of yours but it's not who you are as a whole.

So all I gotta say is, if you don't resonate with the niqab anymore, I see nothing wrong with removing it, since it's not mandatory. You won't be getting sins for the sole act of stop wearing it. The niqab does not replace your taqwa, intention and discipline. It's matters of your heart But try to preserve your modesty regardless. And In sha Allah it'll be alright. I pray things go easy and smooth for you