I am wondering if I need to do things like Defragmentation and Clear Cache, to keep Ubuntu running smoothly like that done on Windows?
Actually Fragmentation is there in NTFS where you install Windows, so you need to do defragmentation. while coming to Ubuntu , we install it in EXT type partitions & they don't need defragmentation because EXT not stores the data in fragmentation.
So no need of defragmentation for Ubuntu.To know more about fragmentation
while coming to cache , its a single word but connected to all areas of Ubuntu.
If you are running out of space , by clearing cache you can save your space.I do use bleachbit to clear cache that will remove apt-get cache , autoremove , autoclean , browsers cache and other in Ubuntu system. Removing old kernels also gives you more free space.