"Best" is subjective, it depends on what you value. Thermo Block will lower the booster's percentage gain, but allow you to improve the Reinforced mod's low thermal resistance. Super Caps will increase the percentage gain further, but lower all your resistances.
I've personally found the vast majority of the experimental effects for Boosters (or HRPs, anything dealing with defensive stats really) to be either a net loss, or such a minor gain they're not really worth bothering with, so I use Flow Control for the reduced power consumption. A-Grade HD Boosters take a whopping 1.5MW each. Shaving 10% off all of them saved my 'Vette 1.05 MW which, combined with Flow Control on the SCBs as well, freed up enough power to go Armored on the PP instead of Overcharged. "Best" mod for my situation.
As for Compact Comps, I just trade for them, as I do most G1 mats. Get some Prop Comps or CDC from a Conda/Mission/HGE, trade for dozens/hundreds of Compact Comps.