What is the difference between capacity use factor (CUF) of solar power plant and plant load factor (PLF) of coal based power plant? Can we compare both since they seem analogous?
Plant load factor and capacity (use) factor are two names for the same thing: the ratio of mean power to rated nameplate capacity.
Capacity factors between very similar or identical technologies that are serving a similar role on the grid, can be comparable: e.g coal and gas CCGT plants both working as baseload, or both working as mid-merit, or both working as peakers.
However, capacity factors between very different technologies, or by plants serving very different roles, are not comparable. So no, coal and PV capacity factors are not comparable.
Wind capacity factors in the short term are mostly driven by weather, but over the long term are mostly driven by the farm design, as I explained elsewhere in more detail, previously.
In theory, all other relevant things being equal, a higher capacity factor is better than a lower one. However, all other relevant things are almost never equal, and it's rarely as simple as higher being better. Indeed, there are some fairly common circumstances where higher can be worse. If a wind farm was achieving 80% over the medium to long term, that almost certainly means that the windfarm designer has made a very expensive mistake - they should have designed for 20-60%, depending on the particular local weather and economics.