Yes, Vivo S1 has dual 4G support. You can use 2 4G network sim cards at the same time.
No. Vivo S1 is not a waterproof mobile phone. However, plenty of covers available for the mobile which can protect from sudden water splash.
Vivo S1 has ARM Mali G72 MP2 dual core GPU.
Vivo S1 has 6.38 inches of AMOLED Full HD plus display. It is further protected with Corning Gorilla Glass 5 level of protection. The mobile has a 90% screen-to-body ratio and has 19.5:9 aspect ratio. Vivo S1 offers 404 PPI of resolution.