AMD tried to convince OEMs with their Temash APUs (4x 1GHz + 1.5GHz Boost in Turbo-Dock) - didnt worked out.
A Tablet should not use more than 7-8W - the lowest Ryzen 3 2200U has 12W
if you wish i can try to underclock my Ryzen 5 2500U to 7W and give some benchmarks - what i can say is that at 5W he clocks itself down to 400MHz... - that would not be good for Win-Tablets...
PC: R7 2700X @PBO + RX 580 4G (1500MHz/2000MHz CL16) + 32G DDR4-3200CL14 + 144hz 1ms FS P + 75hz 1ms FS
Laptop: R5 2500U @30W + RX 560X (1400MHz/1500MHz) + 16G DDR4-2400CL16 + 120Hz 3ms FS