Hmm, much to consider here.
1. Minimising Path Length Difference (PLD) - You want your tweeters to be the same distance from the listener as the midrange, and if this is not possible you want it to be as close as possible. This is not as
important for the midbass, but I would still try to get as close as possible for best results. Fancy processors with time alignment are great, but that should be used only as a last resort - there is no substitute for true physical time alignment.
2. Position - You want the tweeters as close as possible to eye height, and as deep in the corner as possible. From my experience this helps a lot with staging.
3. Angle - You want the angle of the tweeter to be as close as possible to optimal for that specific tweeter. If the tweeter has a significant naturall on-axis rolloff, you want to mount it as much on axis as possible. If it has a slightly rising natural response, then you might benefit from putting it on a slght angle to help neutralise that. In the case of the Focal tweeter, I'd say about 30 degrees off axis is optimal.
Personally, my first priorities are usually points #1 and #3. I find that timing and overall linearity are absolutely critical to having a nice even integraton with the rest of your system. Issue #2 is almost important, but IMO not as much so as the others. Just my personal opinion there