Hi Futurelookin,
I had a similar decision to make in January for flights to Australia with Skyscanner's results showing flights by e-Travel.ie considerably cheaper. Similar to your experience they made it clear that they could not provide any email or phone support if I did not purchase their After sales package. I phoned their Support number to get a feel for them and the lady I talked to was very polite and helpful. I also checked the costs of the flights booked directly with the carrier (British Airways) and they were considerably more expensive.
I booked the cheapest option through eTravel.ie, received one email from them as confirmation (which also touted the After Sales package) and immediately saw my flights added to my itinerary on the British Airways app. All my further interactions were directly with BA over the app i.e. Check-In, Boarding cards etc
This is just my experience going with the cheaper option, it may have been quite different if I had run into issues.