Introducing hierarchy is for your organization of the design and better readability, etc. Physical placement, although it follows the hierarchy organization doesn't really care about hierarchy in the drawn schematics. What I mean is that for example you can physically place two transistors such that they abut each other but still come form different hierarchical blocks in the schematics.
This being said, it is a good practice to keep transistors generating the bias voltages close to the transistors receiving those bias voltages and preferably in the same diffusion (OD). You can, for example add same size dummies between the generating devices and the receiving devices to cover the distance but that distance should not be excessive. Maybe worth of no more that a few dummies.
A good practice is to distribute currents, instead of voltages for biasing stuff and then from those currents generate bias voltages locally. Thus, you can have one master bias block from which you send bias currents to local bias blocks. In this respect, going to your first circuit, it is much better not to get the voltage Vbiasp, but to get the current that goes down to the NMOS diodes.