They do support changing the hard drive yourself in the non-retina Macbook Pro. I think it requires a torx screwdriver to attach and detach the drive from the mounting frame but that's not really a big deal.
If you want to use this at your desk almost all of the time I think a refreshed iMac will give you the most bang for your buck. Counting on a laptop to run at peak performance for long periods of time while closed on your desk isn't super feasible.
If you just want decent performance and the ability to use it around the house and maybe take it with you on a trip, the Macbook route might be a better fit.
Isn't refurbished just the Macs that where sent back because they where faulty, but apple fixed em. Kinda a bit weary about buying one of those because of that. Also do they come with the Keyboard and Mouse / Track pad too?
"They are in 100% working condition, and are then sold as refurbished product. As these refurbished products have been unpacked and manipulated, they might however exhibit some minor cosmetic imperfection, such as scratches, marks or discolorations."
That don't sound to appealing to me. If the rates of that happening are Very low like Sub 5% id go for it but I am not sure on that.
It's possible it does, it wouldn't be the first time Apple has, for whatever reason, not allowed configurations up to the max spec.
I just watch a bunch of videos on upgrading them to 16GB and it seems to work ok.