Is there a type of doctor that just deals with maternity medical issues but is not a high risk pregnancy doctor?

Yes: A ob/gyn can deal with those isuues, as well as a high risk ob/gyn who also can deal with them.

Yes: All docs who practice OB understand medical issues in pregnancy. This is important to screen all pts & to not miss a serious medical condition that may affect a pregnancy or require more specialized care. There is a large overlap of docs who understand maternity issues - then they individually decide which ones they want to follow & which ones benefit from a high risk physician's care.