I haven't physically paired in years. Even before the pandemic I'd often be screen sharing with someone across the table from me. We'd just be positioned where we could see each others' faces and our own screens.
These days it's all fully remote. And that's worked out incredibly well since my team has gotten more and more geographically dispersed. The few that were before are now always in the loop.
I haven't done it full time in a while because my responsibilities other than implementation take too much time.
I'm old in my team and when I can, it works well for me. I share my experience, keep software focused, etc. The younger, high performers teach me new tools and tech. The fresh folks learn more how to think and do work from us. Stuff like that it's not just about making something work, but making something maintainable. I probably teach as much backspacing through a "clever" idea I had, than by writing anything. That and how to break a problem into chunks. Then reevaluate that and make it clean.
Pairing is also great for the more ops side of things. I think in a lot of ways you get even more bang out of it there than programming. Have 1 person do the work and a newer person improve the docs as they go. Then flip for the next iteration, with the new person driving and the experienced one helping and tweaking docs. Call out places where automation could replace procedure and get them in the backlog to be prioritized later. The same pair can pick up those stories when they come back around.
I have experienced some of the pains of this list. I worked with a guy who I joked "painted" code. Lines just growing and shrinking like a horizontal EQ. It was dizzying and unpleasant. I often just checked out and pointed out missing braces every once in a while.
Same guy brings up an issue not mentioned here for physical pairing: make sure you bathe. Ugh.
Also, make sure you're rotating teammates. Sticking in 1 pair can be nice if you like the person... for a while. But it can ruin a friendship if you do that for months.
I think the real keys to success there are in luck and management's hands. Make sure you have a mix of maturity and skill sets, and have engaged curious people. Slackers and, uh, "dim" people drag everyone's morale down more in an environment like that. I've lost those teammates and seen team productivity grow. At the same time, it's hard for a team full of people with little to learn from each other to stick with it. It's more engaging when you're teaching or learning or ideally both.