Overall, I like your setup. A 20 long with a bakpak and 130 watts of light will give you a lot of options.
Your salt mix has all the buffers you will need. The only substances that are consumed in significant quantities are calcium and carbonate. These will need to be tested and added routinely in a balanced way. By balanced, I mean that they will need to be added in roughly equal amounts, because they are consumed equally to make calcium carbonate by corals and coralline algae. The easiest way is to use a two-part additive like ESV B-Ionic.
Another, cheaper, option is kalkwasser, aka calcium hydroxide or pickling lime. What I used to do when I was keeping a 20 was to use a saturated solution of kalk to replace the water lost by evaporation. You have to drip it slowly, because it will drive your pH up if added all at once. Fairly simple, very cheap, and pretty good for moderate demand.
If you want a more complete description, I can post a few articles.
I have not bothered with traces, just replenishing them with water changes. If I can't measure how fast they are being depleted, I don't feel comfortable adding them.
In a FOWLR tank, the biggest consumer will probably be your coralline, and the demand won't be that high. You will probably be able to get by with water changes and small doses of a two-part additive.
Until you get corals, you might think about just using 65 watts of light. It will keep the heat down, may prevent a little algae, and your fish won't need 130W of light.