I will still use conduit even in the attic. I did. Wild life can get into attics now and again and they love plastic cable for some reason. But even more the conduit protects cables and makes it really easy to change them. You can certainly use tech tubes, that are cheap and easy to run. Then changing a wire is just pulling a string. I bet one day you will be glad you did.
Another thing for the ceiling speakers make sure you use back boxes.
These are tech tubes.
I prefer grounded steel cable for the speaker wires though. You might think that strange, but speaker cable is a source of hum and buzz,, as it can feed LED and SCR buzz etc, back to the high gain stages via the negative feedback in the power amps.
Ceiling speaker back boxes.
Allow generous sized conduits for HDMI cables. They are very fragile and need pulling very gently.
The other two issues, are the ground plane with avoidance of ground loops and equipment protection.
Ground planes are a whole subject alone and also minimizing buzz and hum from RF interference from LED bulbs, and SCR dimmers etc. It is a real bummer to do a lot of hard work and end up with a noisy humming buzzing system. Without careful planning that happens all too easily. The more channels you add the more obsessional you have to be. Tying in the grounding of cable and Internet systems properly is crucial to avoiding hum and buzz. Good Internet patch bays and hubs are a good plan. Just about everything in the system needs an Internet connection now. Those connections should be wired. Don't rely on wireless. It is a good idea if possible to make your AV system the heart of the Internet system of your house and the same for cable.
Protection starts with whole house surge protection right at your panel. After that if you want further protection then UPS units should be considered, especially these days when electrical storms are more common and violent.
Time spent on very careful planning pays dividends. These are not simple systems now, and there a bear traps aplenty for the unwary.
When it is all done though it gives the whole family a lot of joy.