I can relate to that. I tried a 4K dual monitor side-by-side setup some time ago (on a Windows PC), but my initial excitement at the available screen real estate was soon replaced by fatigue from eye and neck strain. Turning my head several times a day and forcing my eyes to refocus on a new target left me sore after a day's work.

Command/Tab is now my preferred way too. I've also come to really like Stage Manager on Mac and I don't feel like I need another screen anymore.