There is not the one windows alternative, there is a whole bunch of distributons that are all pretty good usable on the consumer space. For example manjaro, Linux mint, zorin OS... You can try them all out using live usbs to decide which is the best for you.
I strongly overclocked my raspberrypi 4B to 2Ghz at the cpu, 750mhz at the gpu and 3.8Ghz at the ram.
I'm using a active cooler to cool cpu etc.
!!!Do not try this with out an activ cooler!!!
!!!Overclocking can harm your Pi and your waranty is instandly gone!!!
I overclocked to pi adding...
That doesn't make any sense. Xubuntu is a flavor of Ubuntu just with another desktop. So it doesn't make sense to make a server version of a flavour of Ubuntu to make tasks for which you just don't need a desktop.