I dont like them for the simple fact that when I called them to ask a specific question about one of their products, they literally told me to google it. Ive called GH, Botanicare and DynaGro many, many times with questions and have found their reps to at least be very well informed about their own products.
Another issue that I have with Humboldt is that their fertilizer lines are just ripoffs of products already being offered by other companies. Their 3part is a GH ripoff, their Master A&B has the same NPK ratio as Sensi, Connoisser and several others Im sure. Their boosters are nothing new and just another attempt to slice into the Liquid Karma, Calmag, rootzyme, and carb additive market. Cool labels but thats about it.
Id highly recommend DynaGro for beginners. Just make sure you have a pH pen and a TDS meter then hit me up for a suggested feeding schedule for dirt or hydro. DGs nutes will fry plants at normal doses because their highly concentrated so thats the only thing Id tell growers to watch out for.
In regards to your feeding rates, don't use more than a tsp per gallon of DG's base nutes. I'd feed at half that with 1 tsp of protekt to balance the pH per gallon.
Ive used other ratios throughout the years because thats what the brands gave me that I used to use. Ive seen the best yields across all strains from DynaGros roughly 1-3-2 ratio (which is what results when I mix grow and bloom). It just seems to be a nice balance that offers enough N to keep them green while not overloading the plants with too much P and K. Feed at modest levels and youll be putting your plants in a position to pull up what they want, when they need it. It works for me and Id recommend it for others, but Im not saying use this ratio or GTFO.
In regards to the different nutritional needs of the different strains, I really don't think it varies that much. I've found that training, pruning and shaping to be much more strain dependent than even feeding levels.