You dont need to do any blending of the seam with a french white tip, all you need to do is take a white block and gently remove the shine off the whole tip.
As for tips with a well or no well i guess its down to personal preference and what works best for you. Personally i found when using white tips the ones with a well in left a slight shadow.
I cant remember what make the white tips was but i had some with no well that had a deep smile, lovely C-curve and was ultra thin and as far as working with a white tip goes they was a dream to use.
So once you have done a thorough prep of the natural nail place your tip and all that is needed then is to remove the shine.
Hope this helps