One thing I have noticed in Safari 10 is the text on websites is smaller and there does not seem to be a preference, as in the old days, to set the minimum font size.
You can send feedback to Apple
here. I just submitted a comment, to the effect that I won't be upgrading to Safari 10 until this is fixed.
There is no setting for minimum font size in Safari 10 or Safari Technology Preview. However "Zoom" is an alternative that is some ways superior. When you zoom a page to a comfortable size for reading using View ➠Zoom In, ⌘+, or icon on a customized tool bar the zoomed view persists at least for that site even if opened in different tabs or windows. The advantage of zoom as opposed to minimum font size is everything on the site is zoomed appropriately and no matter how the site is coded there will not be any text cut off or overlapping an adjoining field.
Personally I would prefer the ability to set a default zoom to a minimum font size.
