Be advised however that the phylosophy can be slightly different for Delta 3D printers and that you might look for another type of guide if you own a Delta 3D printer.Also the described marlin firmware is from 2015 August 24th so if you want to update to a newer version be advised that some modifications might be needed that are not covered on this guide.
For All In One hotend, you will need to lower it down to 250 in order to avoid big overshots.
Near line 268 you should find the parameters to enable/use pid function for heatbed.
If disabled you are going to use a « bang-bang » temperature control logic (see wikipedia for more details: https://en.wikipedia.org/wiki/Bang–bang_control) It’s better to use PID mode for heating element that are compatible with this mode of heating such as Hotends and 220V heatbeds driven by SSR.
Avoid using PID mode for standard 12V 200W heatbeds because the power supply might not handle it very well.
Check what hotend you have and uncomment the 3 set of values corresponding to your hotend.