Hi, bit of a simplistic answer here but a while back I contacted support about this, when I too was seeing slow response in the Live Editor Matlab R2019a. Very annoying. However, I'm using a Surface Book 2, (i9, 256GB SSD, dedicated graphics card but forget the specifics) and the best advice I got was increasing the Java Heap Memory in HOME (Tab)> PREFERENCES (in the Enviroment section of toolbar)>MATLAB>GENERAL>JAVA HEAP MEMORY. I cranked mine up to an arbitrary 3677MB and that reduced the lag enough to be funtional. There is a bit, but it's not as horrible. the max is something like 4077MB (for me) and it has almost no lag.
Anyway I don't know the drawbacks of doing this, but it makes my life easier and I hope it helps yours too.