My wife has a 6a. A few things that she has noticed but not deal breakers. After installing a glass screen protector the finger print reader is really hit and miss. I went to enable face unlock but Google doesn’t allow it on the 6a. Custom ROM would solve that, however I don’t know about graphene. Not the best cell reception. Not a huge case selection. At least compared to non (a) versions. Battery life under heavy use is just ok.
I use the professional version of Onshape for work. If you create all the parts that relate to each other in one part studio. It can be all contextual. So changes that are made to one part can automatically update on the mating part. I would recommend you watch onshapes introductory videos on their website. That are surprisingly informative and short and to the point. Also their help guide has almost a video for every tool in it.