I have a XP-Pen Artist 15.6 pro drawing display , Surface pro with gpu, and ipad 10.5 the experience regarding drawing goes like this:
Ipad Pro > Artist 15.6 pro > >>>>Surface pro The Surface pro has little to no pressure curve compared to the other two, has pen jitter, lag (even the Artist 15.6 pro connected to the Surface pro doesn't lag, it's not the processor, it's the N-Trig tech that lags) .
ipad pro has higher refresh rate(120hz) which results in lower input lag when drawing. Also the apple pencil supports a wide range of pressure sensitivity.
the Artist 15.6 pro has pen tilt and pressure senstivity but need to connect to a laptop which is not portable.
Get a desktop(a dencent one would be about 1000 euro) and a second hand ipad pro 10.5(500Euro) + a Artist 15.6(400 euro) (not pro) you're even gonna save money in the end .