The regular inawera strawberry concentrate(truskawka), is recommended from the makers at 2%(it used to be 3% for the older strawberry e-aromat truskawka, but they enhanced it 2 years ago thereabouts into concentrate version with 2% recommendation).
They base there recommendations on a 50/50 mix mostly and from an average of a bunch of pre-testers of the flavor on there forum.
I've also found that 3% for the old(e-aromat) and 2% for the new(concentrate) is spot on for me, but i've also only tested it on a 50/50 base and not anything higher in vg. It's very good imho, btw.
Many state "regular inawera strawberry", and instead talk about the Tino D'Milano version, since it also states inawera strawberry and the Tino D'milano, is written in small on upper left only I believe, or used too... That version is likewise very concentrated, and recommended as 1-2%, and i've only tested it at 2%, which was fully potent, but just a half-decent not very natural candy type strawberry to me...
The shisha has something in it's flavor profile that i'm not a fan off, and it's e.g. very detectable just from smelling the bottle, but I admit to most probably being the odd man out, since many love and rave about it

(I don't mean it smells or tastes bad at all, but just some slight undertone that I would rather be without or how to put it...)
Before I wen't to unflavored, strawberry vapes was my absolute favorite vape...