Which is the best processor and RAM for a smartphone?

This appears to be a generalised question. Having more RAM will ensure you better multitasking. You can run a number of applications simultaneously without having some of them closed.
On the other hand, better processing power helps you get lag free operations. The apps and games will load faster and run easily. Striking a clear balance between the two will serve the purpose well.
Processor is comparable to the brain and RAM is equivalent to memory.
In connection with your query, having 3 GB RAM with low clock speed would not be better than the 2 GB RAM with more clock speed. Having 2 GB RAM over 3 GB will not make much of a difference in case of mobile phones.
So, my advice would be to go for a 2 GB RAM with 1.7 GHz processor. This will allow you to have the best of both worlds!

Processor speed and RAM both are equally important. The whole concept is about processing as much memory as quickly as possible. In reality, both RAM and the processor work together to affect computer performance.

Good processor with good amount of memory (RAM) is desired. But heavy memory with a low processor would not help much. Hence 1.7 GHz octa core processor with 2 GB RAM is advised.

Hope it helps.