you have blooming additives, which usually are PK booster.
Then you have 'supplementary' additives, which don't contain nutrients, but may have various anti-stress agents, biological stimulants, amino acids, vitamins, etc..
You also have a category of beneficial bacteria and fungus.
Finally, you have 'enzyme' products, which help break down dead root materials.
It depends what you want really, probably a PK booster will give the best results as its direct nutrients, the anti-stress ones may help round out your edges for transplants or stresful conditions, depending on your grow medium type bacteria/fungus would be helpful too (soil and coco grows mainly)