Passing the option DetStrategy => Symbol controls how certain functions compute determinants (or in some cases, rank). For all methods, Bareiss, Cofactor and Recursive are valid options. The first two come included with Macaulay2, the third is just a call to recursiveMinors.
Additionally, for the methods getSubmatrixOfRank and isRankAtLeast, one can also pass DetStrategy the option Rank (the default). Not using Rank tells the functions to check rank by computing the determinant, instead of using the internal rank function. This is not usually recommended, but sometimes it can be effective.
The object DetStrategy is a symbol.