I’m using a 2015 15" MBP with an LG 34UM95-P at both work and home. The display is 34" 21:9 with 3440x1440 native resolution. I connect the display to the laptop via Thunderbolt 2, and use a USB mouse/keyboard which remain plugged in to the monitor indefinitely - they are relayed correctly by the TB2 cable without any additional config, as are my external speakers which connect to the monitor indefinitely via 3.5mm jack. It’s basically a rather nice monitor with built in KVM capabilities. I keep the laptop closed in clamshell mode, but out of personal taste rather than for performance.
To expand on that “KVM” sentence, at home the display is shared with a Windows 10 desktop which connects over full-size Displayport, and uses a secondary USB A-to-B cable to use the mouse/keyboard. Sound again routes correctly to the speakers over the DisplayPort cable. I just switch inputs on the monitor and video, audio, and input peripherals all make the jump accordingly. Very pleasant.
Small caveat - LG offers a nearly identical model of this display without Thunderbolt support, which is way less useful to OS X users IMHO. It’s definitely much cheaper, and I think it comes with a
-C suffix instead of