Well if you have a good phone for those emulators such as an iPhone 5. I had an android phone that was very low in terms of specs and it was capable of running many heavy ds, n64, and ps1 games at good speed. Imagine an android phone such as a galaxy s3-4-5. Also I don't like retroarch, in my opinion I prefer separate emulators as they seem more stable and suitable to me.
oh haha well i usually play DS on my macbook cause its 100% and mainly cause the big screen ^^