Ok..with a Plus you have only 1 more module you can add. If you have a net module then that makes 4...
Rule of thumb for planning:
Each PC4 can pull a total of 15 amps.
Sockets 1 and 4 on a PC4 are mechanical relays - they have a limit of up to 8 amps each socket (d0n;t exceed the total PC4 limit of 15 amps)
Sockets 2 and 3 are electronic relays - they have a limit of 3 amps.
So in planning, calculate your load and combine like timed items (ie lights, pumps, ect).
calculation is easy and use this as a guide.
Amps x volts = Watts.
SO take a 150w heater, and assume 115 for you voltage. Always best to take the house average even though it may vary a few volts.
A 150W heater divided 120v = 1.3 amps
Your MH lights are around 2.2 amps each so you could gang them on Socket 1 or 4 of a PC4 if you wish.
Your Koralias are all 6w so negligeable. approx 1/10 amp each Gang 2 and 2 if your going to use the wavemaker function.
Yor T5's are approx 1/2 each..negligeable there too.
Return pump and Protein skimmer on their own socket. This allows you to use the standby modes for feeding and maintenance and set independant controls.
Heater on it's own socket so you can program the temp ranges. For the heater, if it has a thermostat, set the thermo stat a degree or 2 higher than what you want your upper limit of temp to be...then prgram the RKL for your optimal range...this way if for some weird reason the RKL had issue, the thermo on the heater acts as a small backup assurance.
Hope this helps.