Hello. Very first post on here. I ordered some G890 and G969 semi dwarfs rootstocks I am going to plant in April. I looked at several different websites for information regarding the rootstocks and they gave me various different heights that they grow. I ordered them mainly because they don’t take trellising which is something I do not want to deal with. But with what I found out they can range from 12 - 17 foot tall. I want them to be small enough that I don’t have to do a lot of pruning so I thought about planting them closer together. 12 ft per row and 15 ft in width. I figured that they might not grow as large. Upon doing some browsing around on here however I have heard a number of people say that you would have to do more pruning at spacing around that range. Would that help ruduce pruning and how much would it impact fruit output? I will be using Jonathan Golden Delicious as well as Red delicious. I will be growing them mainly for use as sweet cider. I just started growing fruit trees last year so I am far from being a expert.
Those are both middling size trees. I would not plant them close. You will run into density issues with the mast and drip line of the roots.
There are lots of folks who keep M111 down to the 12 foot height for easier picking. But I’d guess that will require more pruning then less. M111 is a bit bigger then those two.
Do not despair though. G.890 and G.969 are the two top rootstocks going. G.890 likely a better home/farm gate tree; G.969 the best high production tree.
Welcome, Tanner! It sounds like you’ve already got some experience with fruit trees. 
For size control, just remember:
Dormant pruning encourages vigorous growth.
Late spring/Early summer pruning restricts growth.
If you keep your pruning limited to the right season, you’ll find it manageable.
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I work at a small orchard on Saturdays. I have been doing that for a couple of years. I try and set aside a hour of day to dedicated to researching my various agriculture persuits.
I will look into summer pruning. Wouldn’t that increase disease risk because the weather is warmer?
I flagged the spots for the rootstocks yesterday. I decided to do the normal 15 ft in a row and 17 wide.
Depends on the specific weather and local disease issues. Any pruning wounds are gonna heal faster when the trees are actively growing vs. dormant though.