Thank you so much for taking the time to respond. I'm doing all this for two reasons :
1) I'm not just asking for myself. I have a partner that is at much lower bf% (18)
2) I'm trying to educate myself so that I understand both these in order to use both at the correct times hence asking for help on calculations.
I will do RFL first now that I understand that but may suggest my partner to jump into UD2 shortly after.