1st time buyer wanting to do it right the first time

There is no 'right' in a absolute sense,to make small niggles 'right' will cost big time if it means a change of rig.
make a best guess and live with it,because as we go though the rv life things change we can't anticipate -change in health ,mobility,partners,family e.g. grandkids coming along? often?
Funds unlimited?
Sooner or later we settle and make do.