How to replace the nozzle in my hotend assembly? What should I take care of to replace the nozzle of the hotend assembly the right way?
What kind of data, precautions, tools, steps, and verification are important for replacing the nozzle?
The procedure seems straightforward but tutorials differ greatly and seem often incomplete. Online videos are great but long, sometimes misleading, and difficult to compare if they use another printer model.
For example:

This Prusa 3D tutorial starts from heating the nozzle to 280 °C, which is dangerous for some hotend setups. Also, it is created around a direct drive extruder, so it does not advise to what to do with a Bowden tube.
Another Changing Nozzles &amp; Bowden Tubes video seems to be a great tutorial but advises heating only to ~210 °C. So I need to make sure I know my hardware limits first? Should I take something else into account about temperature, or just act by experience, starting from 230 °C?
Is that heating mandatory, or only when there is residue filament inside? If there is something to consider about replacement nozzle before installing it, or cooling down again, like PID calibration?

So I am looking for a general overview: what should I think of to be in control? And maybe a bit of why, but not necessarily how. (As always, each detail may be a separate study, so please don't to fall into troubleshooting, which could be done in separate questions like E3D V6 nozzle seized into heater block).
The exact procedure depends on the design of the printer.
After unloading filament, remove and install the nozzle at the highest temperature you will run.  Otherwise, you will not get a good seal between the nozzle and heat break if you depending on tightening at lower than operating temperature.  A bad seal allows the filament to leak out (oozing).    Tighten and untighten the nozzle with wrenches on the heat break and nozzle.  The heat break is easily damaged if tightening too tight into the heat sink, but you need a tight connection between the nozzle and heat break.  This means the nozzle must tighten against the heat break and not tighten against the heater block; thus space between the nozzle flange and heater block when tightened against the heat break.
Note: If you had oozing, it will glue the nozzle and heat break to the heater block.  Heating the hot end will often allow you to remove the nozzle.
Note the electronics of some printer models can be damaged by shorting the nozzles to heater leads, thermistor leads, or even a metal bed.  Check for your model.
Running the hot end at 250 °C or above requires an all metal hot end (a heat break without Teflon) or the Teflon will degrade.  This also applies to Boden tubes that run all the way to your nozzle.  Look for instructions related to your Boden tube.  Go to max. temperature for operating with Boden tube, then you usually clamp the Boden tube in place so that it forms a good seal.