Each parent provides one allele for each gene. The dominant traits will be displayed in the f1 generation unless they both happen to have the same recessive gene. Some alleles combine to create a mixed trait (like a white flower crossed with a red flower, creating pink flower progeny). True f1 hybrids borne of two distinctly different unrelated true breeding strains will display a uniform population. Cross two f1s to create the f2 generation which will show lots of variety compared to the f1s. F2 is when the recessive genes come out to play and where the real fun begins.
If you're crossing two f7s, assuming the breeder made good choices along the way and matched them well for whatever traits they were chasing, then yes, the gene pools will be fairly limited. But there will be recessive traits in each and they will come out in the f2 generation. Many traits that we seek aren't determined by just one set of genes, but many working in unison. So you will have all these combinations that you've never seen, smelled or tasted before from either parent, as well as some that will show similarities to the each parent.
I hope this helps. And I'm no science wiz, so if I got anything wrong please correct me. This is just my understanding of things from years of reading and a little bit of experience.