In your case there would be no difference playing in 720p/1080i/1080p. The max resolution you can display is 1280x720 (720p), so anything higher than that and it's overkill. To your TV there is no difference, and would not cause for it to "work" harder if it were at a higher resolution.
If you're TV is 50", go ahead and set your player to 50". For your color, go with 4:2:2, as 4:4:4 is usually considered overkill and not worth the extra bandwidth since our eyes are more sensitive to color than to light. For your deep color setting, go with 16-bit.
And as for the 24p, if you want more of a cinema look, enable it. Otherwise you'll be running at 30p, which is slightly more beneficial for action/sports.
I would set your blu ray to output to 1080p (it's native resolution) that way you're not down converting to 720p from your bu ray and then reconverting to whatever resolution your tv is (most likely 1024x768). The less converting in the chain the better.
Both of these answers are great, so no offense with the 'Best Answer' selection thingy.
I do agree with getting rid of the double converting steps in the chain, I did not think about it in that way and it's probably why I actually have to wait sometimes for the next chapter to load in the disc. The 4:2:2 option is also noteworthy, another reason why my TV seems to be struggling. And yes, it really is struggling. My friend has the same player now and his 1080p Plasma has no loading delays.