To replace dual monitor productivity, 34'' is recommended.
At 34”, you start to have more than enough room to work, and resolutions like 3440 x 1440 give you enough space to open up three or four browser windows, documents, or applications side-by-side or tiled without text getting too small to read and menus impossible to navigate. Plus, since the 34” ultrawides are usually flagship models, they include all the ports and connectors you’d ever need, VESA-compatible mounting, auto-rotating and fully adjustable stands.
The Bottom Line: If You Have the Cash, 34” are a Great Alternative to Multiple Monitors
for 29", naah - not much, Imagine what additional real state you can have with 34".
But if you still want to go with 29er LG 29UM65 29” would be best choice; for 34" LG 34UM95(I know its almost double the price).