Resources to Add in an Isolated Pblock

It is generally advised to add all the available resources i.e. Programmable Units (PUs) within an isolated Pblock (except those that are needed for the fence), even if the logic tile/PU is not used in the design, because excluding them also excludes using their respective routing resources. Failure to do so, while not an error, might produce designs that are very difficult to route. This is true even for the I/O clock buffers.

However, in the Vivado tool, BUFGs and BUFHs must not be included in the isolated Pblocks unless you want the global clock isolated (not advisable unless the design warrants it to be isolated). All other components must be included.