I drew chair conformation of both with $\ce{Br}$ in axial position, so it can undergo E2. In 1 I got $\ce{^tBu}$ in axial position, in 2 I got $\ce{^tBu}$ in equatorial position.
Would it be correct to say that because 2 is more stable due to bulky group in equatorial position, it would react slower in E2?
For the second part of the question I suggested SN1. But then how would I know which would be faster in this case, since the $\ce{Br}$ does not have to be axial?