I usually only play MTTs or SNGs.
As I'm beginning all over again (and unfortunately still making some of the same donk mistakes, my bad) I tend to focus on one table at a time. I like to find the bad playing LAGs and try and let them bet their chips of to me, and it takes time to assign tags to players at the table + make notes on them. A good LAG player is different matter - real hard playing against them.
However, I'm experimenting with playing 2 tables now and playing more tightly, and using strict Push/fold & Push/shove charts to see if I can smooth out variance to get into the money more often. It's only an experiment.
I do notice, however, that proven poker players who stream almost always multi-table.