Specifically strength we're talking about here.

Both in the same sentence are usually often referred to as 'kickstarts' and a nice bulker such as test e to solidify the gains - especially from the dbol.

What about Prop being a fast acting 'cutting drug' - Continue with the prop at 100mg/day to solidify strength gains, or switch to test enanthate 500/wk?

Estrogen plays its role I would suspect.