First, I'd generally recommend not trying to do both planetary and DSO imaging with the same gear. It can be done, but especially if you are a beginner it will be a challenge you may not enjoy. The equipment choices and technique tend to be at different parts of the AP spectrum.
If you want to do good imaging with an SCT, you get one of the CSCTs (Corrected SCT) like the EdgeHD and that means that even with the 8" on an AVX your budget is blown.
For imaging DSOs? Unless you are expert, have really good equipment, and really want/need to go for the really deep and dim DSOs you should really consider keeping the focal length to less than 700mm and even shorter focal lengths make it easier/better.
The 8" CSCT will have a native focal length of about 2 meters. That's not bad for planetary but it will be difficult for DSOs because we generally don't like doing lucky imaging on DSOs and the tracking and "seeing" problems get much worse with that kind of focal length. You can get the focal length down to about 800mm when Starizona starts selling their 0.4x reducer, but you'll still be in the challenging/frustrating range of focal lengths - and doing it with an AVX mount which some find to be merely marginal to inadequate. It can be done, but it might be considered to be masochism.
Those carbon fiber refractors are sometimes lighter than the alternative but that is the only benefit from the carbon fiber. They were touted as reducing the need to re-focus but the reality is that increases the need to re-focus and cool-down is slower. You'll note that the premium telescope makers generally do not use the carbon-fiber for their OTAs even though their buyers tend to be the ones who would demand it if it were superior.
The "ED" series from Explore Scientific are, I think, the FCD1 series. Not really an apochromat when you are doing imaging. Very nice for visual use but a great way to decrease the quality of your images!
If you want to go with an FCD1 I'd recommend taking a deep breath, back away from the keyboard for a few minutes, and re-consider. An Ed-Doublet would probably give you optics about as good as the FCD1 and will do it with lighter weight and better cool-down - and maybe at lower cost.
The 127mm Explore Scientific has a 952mm focal length (which makes imaging more difficult/frustrating) and is too heavy for your AVX mount idea.
Now if you were to get the Explore Scientific 80mm FCD100?: https://explorescien...0-apo-refractor Nice short focal length for easier imaging, lighter weight, faster cool-down, and less cost - with better optics.
If you went for their 102mm FCD100 you are getting into a more challenging focal length but otherwise it should perform fairly well.
I don't think Explore Scientific sells a matched field flattener and over time I've come to the opinion that I'm just not buying a rather expensive triplet (or even ED-Doublet) refractor for imaging purposes unless I can also buy a field flattener which is sold by the manufacturer and matched to that particular OTA. I don't mean just "recommended" I mean matched. Unless it is truly matched to that particular OTA I don't trust it to do the job to the degree that I demand if I'm trying for that degree of optical excellence.
But a quite different suggestion?
If you are a beginner at imaging and you want fast imaging at a reasonable cost? Get the AVX mount and then get the Astronomics 6" astrograph: https://www.astronom...tical-tube.html You'll get more aperture for faster imaging, the weight is pretty nice, and the price is very good. Yes, 6" means a bit of a cool-down time period but it shouldn't be very long.
Then you also get a good coma corrector and you are pretty much set.
The savings means that if you want to autoguide you have some money left over to make that happen. I still refuse to autoguide and I don't suffer much as a result - and I'm not trying to compete with the folk who do autoguide so I'm far happier not doing that.
OK, one other thing? We really ought to know what camera you plan to use. That might change things a fair bit.
Now if your emphasis is on trying to do high-quality imaging? Getting the big SCT and a camera which will do video at a rather high frame rate is usually the ticket. A CSCT is nice but not particularly necessary since you'll probably be centering the planet you are imaging so the regular SCT focusing issues and coma/curvature issues are not likely to be a concern.