Text-only email newsletter

Hi coaches,
I am in the process of building my email list and prepping newsletters. In some of the research I have done, a suggestion was made to have a text-only email vs. one with images in it as the open rate may be higher (not recognized as a “sales” email). I started going through the emails that I subscribe to and saw that with many this is the case- for example, Friday Coach Like emails. My question is two-fold, do you recommend only doing text emails with no images and does a logo count as an image. I want to maximize open rates of course. Thanks for your help!