I don’t think so. Its just do the job. Fit/rotate, rows/cols, sharpening, perceptual/relative, etc. - all there. In the past i use PL for printing occasionally - just works fine. As a long time Epson print layout user, i just use EPL, as i do for ages.
Few improvements thing can be fine in PL, like add ‘layout presets’, etc.
So I have two choices - either carry on with Photoshop / Lightroom and pay £120 a year for the pleasure or buy a forever licence for Qimage at a lifetime cost of £92.
You have lot of choices, like Epson Print Layout, also various software’s can do the job.
Keith Cooper youtube channel - he a guru on printing! And he say: ‘Using Epson Print Layout - the et-8550 IS supported’ Youtube video. Dont get a heart attack if EPL not listed as supported in Epson website.
The reason for forum colleagues say Epson/Canon related software’s, as its works fine, they use it for ages, and they use it ‘universally’. Also, like RIP alike softwares, like QImage not a surprising to come up - for the money they add things: layout presets, better workflow, all is more shiny, etc.
Regarding what cause the lines, hard to say. I guess, its caused by some roller (that’s why its some up in 5cm) or print head (pizza marks), and may more often come up in thicker papers, may also paper feed path also impact (try to use rear slot, etc.). I’m pretty sure, if you go to printing forums, you can find one thing or two about this.
May for start see this thread on DpReview:
https://www.dpreview.com/forums/threads/re-epson-et-8550-thicker-papers.4651849/page-2