Why 3 arms?
I recommend two IF you listen to Mono, so you can go back and forth with no delay in a listening session. And removable headshells. And easy height adjustment.
For me, retired, Inherited 4,000 lps, mostly Jazz (had 2500) actively listening, alone and frequently with friends, mostly Stereo but many Mono.
I started with two arms, then found an arm with a short counterweight section so it would fit inside the dust cover, I’m soooo clever, I couldn’t help myself.
The above configuration was only 1 removable headshell.
Mono on the left, Removable Headshell in the back, play friend’s cartridges, any of mine (I stopped at 8);12-1/5" effective long arm, fixed cartridge on the right, my favorite MC at the time.
After buying a few vintage cartridges, I changed to 3 removable headshells
As we like to say, "I’m Done!"

