Toilets, Sinks, Showers, Tubs and Disposals - offset toilet flange questions

my toilet rough in in my basement is about 16". plumber (not one who did rough in) wanted to use an offset flange. It goes inside the 4" pipe and has an ID of 3". It moves opening 2". he said I could then get 14" rough in toilet. I wanted to know if the offset flanges are problematic. the plumber said that "they" say that 4" may not be best for toilet as the large size means a lower water level and the waste doesn't go down as well as with a 3" and in some places 3" is recommended.

what are other options? chip up more concrete and then use 2 45degree elbows? how far would that move the pipe? is there a way to cut the pipe below the level of concrete I guess you could use a dremel from inside pipe?

I've never has to use an offset flange in a basement but it certainly sounds a lot easier than trying to move or cut pipes under the concrete. Offsets work fine in other scenarios.

Show us a picture of the offset flange he intends to use. If it's the one that has small ears for the closet flange bolts and a huge shoulder on the back side...I'd absolutely not use it.