Before you do anything, either you or a potential supplier must run a heat load analysis. This requires measurements of the glass area, building insulation, size, and orientation and takes into account the local weather. Just taking sq footage will not likely produce the most efficient or comfortable solution. If the calculation comes in-between standard sizes (normal), you'll usually be better off choosing the closest smaller unit. It will run longer, removing more moisture, and even if on the hottest day it runs continuously, the house will feel better because it will be drier. The worst thing to do is have one too large, since you'll be cold, clammy, and spending lots more money than needed. It's much better to be a little warmer on the hottest day of the year, and be much more comfortable the remainder. And, that may only be a degree or two. Because you'll be nice and dry, you may not even notice.
The compressor must be outside, but your question of where the rest goes depends. If you can place ducts in the ceilings of the areas to be conditioned from the attic, then placing the air handler there may be best since the cost of ducting will be minimized.
If the ceiling registers would be too obtrusive, you can go with a high velocity system ($$). These put what almost look like recessed light cans as outlet registers in the ceiling. It uses a diffuser and high velocity to get enough cold air into the room.
If you want to avoid ductwork, have you looked at any of the mini-split systems? This leaves the compressor(s) outside, and some can have up to 3 outlets, each individually controlled. No ductwork to run. The unit is bolted to the wall and depending on the model, is maybe 5" thick. Many can be controlled with a remote, so you do not need to be able to access (except to periodically clean the filters). Mitsubishi makes some nice ones, and others may have some additional recommendations. this allows you to easily only cool those area(s) you want.