A mature pair of clownfish of any species will eventually demand the footprint of about a 30 gallon tank. It'll take a while for them to grow to that point, but bear that in mind.
Damsels and dottybacks are both quite territorial as well. The yellow tail and orchid however are both considered much less aggressive than other members of their respective families.
Would suggest two mature clowns, orchid dottyback (needs lots of live rock caves to feel secure, will be less aggressive. Also comes tank-bred, get one of those). If you didn't get a dottyback or damsel you could probably have 4-5 smaller fish, my personal choices for a 45 would be two clowns, a yellow watchman goby, Royal gramma, and a banggai Cardinal.
I've worked with and bred several different clown species. You will want a shoulder length glove, female clowns of all species bite and even smaller ones can be annoying at best. Do enjoy the salty side though!