Is it recommended/required PCI Planning in network if we change BW, like from 5 MHz to 20 MHz?
No need PCI Planning.
Only power audit is crucial to keep the same coverage.
One more question: is it possible to deploy 18.8 MHz instead of 20 MHz?
If yes, how and what are the challenges?
No need to do Replaning of PCI. It’s not BW dependent.
You have changes in cell reselection priority and inter freq if priorities are changing.
With idle mode, mlb and inter freq parameters.
If it is a requirement.