2-3 topics in-depth better than 10 topics sketchily.
Choose topics that are
Omit unimportant details: ``I will only explain the first step of this proof, the other steps are routine and are described in the report''. ``I will only describe the second step of the algorithm ...''
Simplify theorems/proofs: ``I will prove a simpler version in the talk; the report contains a more general version, whose proof is much more complicated''. ``I will describe an O(NlogN) algorithm in the talk; but it is possible to improve to O(N) using standard techniques- this is described in the report''.
Tradeoff: Bite what you can chew.