Don't over think it. Its important when you have a high tech tank with demanding plants that require CO2 injection, high light and heavy fertilisation. Nothing in your tank falls in that category. My approach is quite simple when setting up a new tank - pick a light intensity that seems right and the light period you want. Run it for 2 weeks and if you see no visible algae turn the lights up a bit. Repeat until you see algae then turn the lights back down to the previous level.
I have 4 tanks and have no idea what the par is in any of them - you can see the result of my approach here https://www.fishforums.net/threads/a-tale-of-4-tanks.463021/
Note: In that thread I say I run the Aqua One at 100%. Since then I have removed the frogbit which created a lot of shade - I have turned the lights down to compensate for that and to avoid visible algae.
