Ubuntu - my 2cents

[MarkHaysHarris777]

Unfortunately Mate-system-monitor (25-30%) and the X-server (25-30%) grab the lions share of cpu. Any thoughts on why this may be the case? Is it to do with lack of Mali support?

No. 

... mali has nothing to do with how many resources ( like cpu % ) are used by mate-system-monitor , or the X-server. The kernel controls directly the resources of the system ( for instance which processes run, in which order, and how much time-slice or cpu % ).  I am of course over-simplifying.

The mali driver is an in-memory accelerator for openGL GLES;  and that is all !  ( um, if you have the 'gears' demo program on your system its 'mali' that will make that work well with openGLES. That's it. 

A common misconception about cpu % is that the number is somehow 'bad' if its high for one or more processes;  this is of course not true. ( it 'might' be true under some conditions )

A background process can 'look' like its using 100% of the cpu , well , because nothing else needs the cpu just now...  but will quickly be reduced in priority by the kernel if something else requires the cpu atm. Also, there are 4 cores active in our little processor. Four processes can be running 100% on their particular core and not affect the other processes on the system which are free to run on the other cores. Very seldom does a process(s) like the X-server , nor the system monitor , cause a performance problem which is systemic !