Firstly, if all you are interested in doing is imaging/viewing the planets, then you don't need the Edge optics, the standard SCT is fine. This is because the planets are small and centred in the middle of the field, so you don't need critical focus right to the edges. If you are looking at using it for wide field DSO photography, then that's a different story.
Generally speaking, you want to match your barlow with your camera. Best practice is to use a barlow to get your focal ratio to be around 5x the pixel of the camera in microns. If you go with an 8" SCT and ASI224MC (with 3.75 micron pixels), then a 2x barlow to get you to f/20 is about right. Of course, if you were already thinking about spending money on an 8" Edge, then the C9.25" non-Edge might be a better buy for the money.
I use a 2nd hand Tele Vue 2.5x Powermate which I find is great. From what I've seen from others, as long as you are not buying the really cheapest of barlows, they are all pretty much the same.
These days, the ASI678MC (with 2 micron pixels) is a popular camera, which doesn't need a barlow at all with an f/10 SCT.
By the way, an 8" Dob on a tracking mount is more than capable of creating great images of the planets as is, you don't need to go with an SCT. Of course, if it's not on a tracking mount then it's a lot more difficult, but don't think that you cannot take great images of the planets with a Dob...
More info in the Planetary AP FAQ on Cloudy Nights
https://www.cloudynights.com/topic/8...-january-2023/
