I just bought a pair of CalTrend EuroSport Covers. They are a vehicle specific 2-tone Mesh that I like very much. The colors fit the dark theme I went to. I recovered the center console lid, and covered the lower center instrument cover for more dramatic effect.(Ha Ha) I'm also experimenting with the door panel. I've included pics and a link that you might need to reconfigure. Well worth $168.
That door panel 2-tone look with Latte UniSuede and Black textured vinyl is the latest adventure. (Yes, I've lost it).
I don't have any seat cover recommendations myself, other than what I see in the forums with Weathertech and Okole being recommended the most often. For the Highlander it seems the 3rd Gen crowd has been most interested in purchasing seat covers, so you may want to use that forum's search tool to locate past threads discussing seat covers. No doubt any company discussed there will have covers that will fit any model year Highlander.
No, and I wouldn't suggest you do. This is so much like scuba suit material but not quite as thick. I bought some specific polyurethane cleaner, but later started using a wet towel without removing the covers. The Collegiate line costs more, but they have plenty of choices. You can stay under $200 for the front and be happy with them.
I recommend you to go for Saddleman's saddle blanket & their neoprene seat covers. I have used both, one in my Ford f150 and the neoprene's in my wife's chevy & i must say both are very comfy, durable. Here's the reference https://www.saddleman.com
I've got a 2012 and currently have coverking neoprene for both 1st and second row, and caltrend for 3rd row since coverking thinks I have a solid 3rd row seat. I went Caltrend after coverking thought I had a solid 3rd row seat, but found the quality was nowhere near the coverking I originally bought that cost me more, so I went back to coverking neoprene front and 2nd tow while 3rd row is Caltrend. All charcoal grey and black