Sorry, typing too fast. The reverse is true, escort is lower risk. EWH
A street walker is lower risk than an escort? That's weird.
Your question is so general that it is difficult to answer. The purpose of this site is not to provide a text on sex acts and their risks. Let me provide a few comments regarding female CSWs and then if you have one specific question (not on and on), I can address it.
CSWs are not a homogeneous group. In areas where they are licensed (Nevada in the US, Amsterdam, etc) part of the licensure relates to regular check-ups. This works in your favor.
A second tip about condoms. Your risk with CSWs who require condoms is lower than for those who do not. Not only because the condoms protect from transmission but also because most often they are requiring condoms to protect themselves from you. turning it around, this means they likely do not have STDs or HIV.
Where you meet your CSW partners matters. A street walker is lower risk than an "escort" working for an escort service. Of course there are no guarantees but this is a reasonable generalization.
Most CSWs are not infected. While they tend to higher rates that persons who are not professionals, nonetheless most are not infected.
As for sex acts, you can search this site to see that some types of sex act are lower risk than others.
Finally, realize that all of the above are generalizations, not rules. thus there are exceptions. End of discussion. EWH