You can use the PCB without connectors and solder the wires directly to the PCB.
However the connectors make installation, testing and repair much easier.
Basic connectors
Mains
5pin 5.08mm grid spacing.
Neutral filtered for measurements, Neutral for triac switching, Line 1, Line 2, Line 3
Triacs
2x8pin double row = 16pin 2.54mm spacing
5V
4pin 5.08mm grid spacing
5V, GND, 5V backup, GND
Keypad
8 pin 2.54mm spacing, pin strip
Display 2.2" ili9341
14 pin 2.54mm spacing female socket and 4pin 2.54mm spacing female socket
Additional Connectors (included)
USB programming
6pin 2.54mm spacing serial0, female pin strip
ICSP in circuit serial programming for bootloader update
2x3 pin = 6pin 2.54mm spacing, pin box
Ethernet W5500 module
2x5pin = 10pin 2.54mm spacing
You can decide wether to plug the module in directly, or connect it with a ribbon cable
GSM adafruit fona module
2x5pin = 10 pin 2.54mm spacing, for flat ribbon cable
WLAN ESP8266 programming
6pin 2.54mm spacing, female socket
I2C, e.g. for RTC real time clock
6pin 2.54mm spacing, female socket
Auxiliary mechanical relays board
2x7pin = 14 pin 2.54mm spacing, for flat ribbon cable
SSRs
2x5pin = 10 pin 2.54mm spacing, for flat ribbon cable
Additional analog inputs
2x7pin = 14 pin 2.54mm spacing, for flat ribbon cable
