What do you think of these two deer? How old do you think they are? I’m thinking the first is 4 or more, and the second is maybe 3.5. The first one seems old enough, but is he legal in an AR county?

I’ll go with 4 on the first one and looks legal but I would want him looking directly at me to make sure before I pulled the trigger.

On the first deer, I’m just wondering whether a deer like that has maxed out his potential.....would he get any larger if he was given another year?

To me the side profile of his head in the 3rd pic shows him to be a mature deer. His body/belly line in the second pic is more of a mature deer. The second buck is really muscular looking like you would see in a middle-aged buck.
Here are pics of a buck from 2018, then second pic in 2019 and then from this year in 2020. Anything is possible with age, nutrition and the right genetics combination. The deer has to have all of that to express his genetic potential.

First one looks 4 and hard to tell as pics going away from you always make them look bigger & even wider. I'd want a straight on forward view before pulling the trigger.
And yes, I do believe he will grow more the next couple years if he makes it.

No way to tell from the pics of the 2nd deer how wide he is but he looks 3 to me in those pics in the 2nd pic of him I'd call him a fat 2 year old.