Pitfalls of SAP MDG-C/MDG-S

Hi,

I  want to understand the drawbacks(Functional/Technical) of implementing SAP MDG-C/MDG-S compared to traditional ECC . I find information of advantages of implementing MDG but I  want understand the pitfalls of MDG-S/MDG-C. I have few scenarios below .

1) Can we create a customer or Vendor in MDG without creating the Business partner.Similar to want we do in ECC(like tcode XD01,,).

2) Can we integrate a custom Fiori UI with MDG solution.

Thanks,

Nagendra.