Determining the temps and speeds for DIY printers?
The short answer is, you use the temps and speeds that give you good results. It's trial and error. 

The temperature number your printer reports really doesn't matter. That's just a process control variable: it needs to be consistent and repeatable, but it doesn't need to be accurate against an independent reference. What you should care about is your print results. 

Some signs your printing temp is too cold:


PLA printed parts have a dull, matte surface
Poor layer adhesion
Extruder stalls or strips the filament at fairly low printing speeds for your extruder and nozzle size


Some signs your printing temp is too hot:


PLA printed parts have a very shiny surface
PLA has a very strong sugary/waffle smell, or any material smells burnt
Stringiness during travel moves that you can't eliminate by tuning retraction
Excessive oozing while the nozzle is stationary off the print
Bubbles or cloudiness in extruded strands in extruded strands even with dry filament


You will also calibrate speeds via trial and error. There are two main speed limits for a printer: how fast the motion mechanism can move the nozzle without running into issues or unacceptable print quality degradation (which is also a function of acceleration settings), and how fast the hot end can heat up and melt filament. 

The mechanism speed limits you have to find via trial and error. Pick a test print you like (such as Benchy) and repeat it with different tuning until you find your preferred limits.

Melt flow restrictions are slightly more complex, because they are a function of VOLUME flow rate, not commanded speeds. Make a large boxy test print (with long straight lines) and multiply extrusion width times layer height times feedrate. That will give you your approximate flow rate in mm3/sec. Generally speaking, every extruder + hot end + material combo will have a maximum feasible flow rate. For example, most "average" hobbyist printers with 0.4&nbsp;mm nozzles and good extruders can extrude about 4-8&nbsp;mm3/sec with PLA. PTFE-lined hot ends are at the lower end, all-metal hot ends are at the higher end. The value will depend on your hardware. But you can do a few quick benchmarking tests to find the limit, and then use that to determine peak feedrates to avoid exceeding the melt capacity of your system.