I would like to migrate Mendix from 4 to 5 without any changes in UI. As 5.18 release is a major release for Mendix UI framework, does migrate to Mendix 5.17 will not impact any small change in UI?
Migration from 4 to 5 requires you to redo the CSS styling. There is no way around this. Moving from 5.17 or before to 5.18 (DX release) or later has no impact. It is your choice to use the new DX styling or not.