I am not a cleaning chemical specialist by any means, but I do have experience on the pro level and what we used for our system/water.

We used sodium hydroxide (caustic) mixed with a bit of peroxide to boost as the oxidizer that would break down soils (krausen rings, hops, proteins, etc.). PBW is an oxidizer as well but does have a formulation with chelating agents to aid in hard water comparability, beer stone removal, and removing metal ions in general.

Citric acid will do a poor job at cleaning soils. Yes, it is a chelating agent, but that’s mostly for helping with eliminating metal ion interference with your cleaner. So you can’t just replace it with an appropriate oxidizer. You’re definitely on the right track with oxiclean and citric acid mix, but aside from that I couldn’t help you out further with improving it.

Honestly, I bite the bullet and buy the 8lb jug of PBW. I have used my current one for about 3 years now with regular brewing (at least one brew a month) and it is just now at a level where I’m considering getting another. That’s ~$50 for 3 years of quality cleaning that’s relatively easy, and I feel confident everything is cleaned very well. Putting it into perspective, I personally am willing to pay $20/yr for easy and really good quality cleaning. I personally never understood the oxiclean recommendations (I have never used it but hear mixed reviews about its effectiveness) when I literally use a couple dollar’s worth for every 5 gallon batch.

A MUCH LESS SAFE and very effective cleaning method is caustic/peroxide mix for soils followed by nitric/phosphoric acid. It’s cheaper than PBW, but I don’t recommend for the home brewer