It is your money. The Seyco solution uses a Rikon Grinder without wheels and they added the sanding sleeves. If I were doing it, I would purchase a Rikon Grinder, take off one wheels and add the JGR sanding sleeve. The sleeves are so easy to change that there is no need for different grits on each side.
I found a Rikon slow speed at Acme Tool. I have purchased from them at least a dozen times with no issues at all. They have free shipping and no sales tax. $130.00. You can leave on the other wheel for when you want to sharpen a lawn mower blade or something else, or you can take it off to mount a wonder wheel.
https://www.acmetools.com/shop/tools/rikon-80-805
If you don't want to mess around with taking off the wheel and guard, you can go for the easy solution from Seyco.
I actually think you are making too much of the 1750 speed. The reason people say to buy a slow speed, is because the other choice is the standard speed which is 3450 RPM which is too fast. I think the variable speed going down to 2000 is close enough. That is what I have. With the choices today, I would go with the Variable speed Delta that you have linked from Amazon above.
Matt