Thanks for the help, Birdy.
I am a newbie so my questions may be stupid.
So say you dont use certain cells (buffers, fillers, etc.) during synthesis.
Can you add those cells back in during floorplanning/routing? My idea is all these dont use cells like buffers,fillers,etc. are used to achieve the given constraints (timing closure, power intent, etc.)
Does it not change the original design as you have now modified the netlist by adding these extra cells to your design? Before you tape out the final gds2 are drc and lvs the only checks to the flow to verify that the functionality has not changed?