Planetary imaging with a 20" Newtonian does not make much sense for so many reasons. Unless you live in an area with incredible seeing all the time its going to be an exercise in frustration. Most locations never get below .25 arc seconds even in fleeting moments. Also a 20" mirror can take a long time to reach thermal equilibrium and until it does you wont be getting good data. I could go on and on.... There is a reason 11" to 14" scopes are popular for planetary imaging. I would recommend a large SCT or a large CFF classical cass no more than 16".
Only way I would consider a 20" would be if I had a temperature controled observatory to house it at over 10000' elevation in excellent seeing conditions on a large custom mount. No dobs need apply.
Elaborate your last lines, because i feel like going larger isn't gaining anything until you have controlled environment or issues are managed/sorted out.
Don't forget the visual part, so because i will use it for planetary imaging as main it doesn't mean i will never use it for visual, and when we talk about visual i hear or read that dobsonians are the best choice and going larger is better, frustration can happen with all astrophotography setup anyway, for DSO i have much more frustration to be honest, and i mentioned before that it doesn't have to be very incredible seeing to justify larger scopes, i see many members in another threads here showing off larger and larger dobs although they live in not optimal conditions, so what makes them to go larger than visual? 20" is still a good aperture, not so much than 16" yes, but it has slightly more, it is no logic to say that 14" has advantage over 10" but 20" hasn't over 16", i know the curve slope after 14" isn't going higher, but it is still increasing, so if the difference could be like %40 between 14" and 10" then it is maybe 10% between 20" and 16", for me that is enough.
I live in a steady seeing area, for me that giving me confidence to have good results and visual, in fact planets mainly Jupiter and Saturn and Venus are very clear, the moon is clearest, so i really don't know how the seeing you have over there, i am happy with the seeing here, and 20" if it won't give me more than 16" then it won't be less than 16" anyway.
Someone mentioned about quartz thin mirror, says it has better thermal equilibrium, so confirm that, and i visual planets with my Mak even up to 600x with nice view, really from the clarity of planets mainly Jupiter i even stopped looking at them, got bored of them, but i know my seeing will never match some areas, i don't care, i want to have whatever i can to use that seeing we have here, and don't forget, the moon is still my favorite target, and i saw images from 20" scopes of the moon, amazing, so my point is telling me that 20" is pointless and it won't give anything good is like telling me a Ferrari is useless in racing because the field isn't good or speed will never go high than another car, but i have to tell you that if i live in a poor seeing condition then even 8" will be like the most i can use, if it is average then 12" can be likely the limit and 14" will be very squeezing, but if it is good to excellent then i swear that even 18" can be mind blowing, so 20" isn't too much far, why i limit myself to 20" if the conditions or environment can help, i said because i got some evidence that seeing in my country can help to go up to 18" without issues, so i want to gamble with 20".
For this topic, ideal planetary scope sounds an answer with some conditions, not a straight forward, OP is living in Ohio, i don't know how is the seeing there, but i assume it just be good for mostly 12"-14", so that going with 10"-12" as he mentioned is just right, but my seeing is better than Ohio, if he is fine with 10"-14" there then i can be fine with 14"-18" here, i will not say we have super clear amazing seeing full year, but definitely many nights, maybe i am too much exaggerated, but i saw people using for example 14" under non ideal conditions with very very nice results, and i also saw images from 16" under good seeing will not say excellent also with nice results, but here it is, i also saw images from 20" that is no less than 14" or 16", not too much better, but not less then mind blowing, i saw crap bad images from all those scopes or even from 1 meter, this is not a standard, the standard is what a 10" capable or or 20" or 30" capable of in different seeing conditions, i am thinking to talk with a prince if he can give me a land on a high altitude Hill in the state of my country, it is not high but the area is almost less civilized, less light pollution than my city, so maybe that area will put the scope in use, i will trust or believe someone in my country told me that they were able to see Uranus in details or at best with 18" Dob, i did read someone has 18" Dob in UAE, i am sure he is smart enough to go with that size if it is pointless.