If you were thinking of self-publishing, how would you, did you, or are you deciding which editor to hire/use?

There are so many on the internet offering their services, claiming to be ‘professionals’. How can the “customer/writer” sort through them to determine if they are really qualified or not?
I ask because I belong to multiple writing groups. Two of which have at least one member who edits for an indie publisher and who also submits their writing to the group for critique. [There are other editors in the groups but I’ve not read anything they’ve creatively written (if they write).]

I’ve read a novel by each of them. I critiqued the novel for one. (definitely wouldn’t spend my $ to buy it when/if it is published. I purchased a novel of the other and had to force myself to finish it. Always hoping it would improve.

Would their writing indicate their ability to edit?

If they were hired to edit a manuscript, would they (consciously or unconsciously) try to make the writing more like theirs? Any experience out there? Please comment.