I think I've discovered what I'm going to do. That's great info kiss. I have shelves in my basement stair area, and this area goes all the way to the ceiling. I was thinking of running conduit inside this area, exposed on the wall (bore holes through the shelves, or remove them) and then into the attic. But you don't run romex in conduit? I'm thinking I need 4 sources, meaning 4 x 14/2 or 14/3 wiring. Should I just run 4 sets of flexible? I read your conduit basics, and It would be nice to run one single pvc or whatever rather than 4. What do you think I should do? Thanks!

Probably time for a picture. You can combine flex with rigid and then off to a junction box and off to multiple Romex wires.
Fish the romex down the walls and you have a JB to work out of.
You can make that box large if you have to. Say 20"x 15" (Kidding), so you have plenty of room.

I think it would be nice to have a chase and conduit would look better too. 4 romex vs. 12 single wires in conduit. The conduit might be more useful.

You could come up and then into a pulling elbow and then transition into flex conduit to a mounted junction box.

I know a great way of doing the transitions, but not sure if it's approved for building use and that's DIN rail and DIN terminals. I'd hate to have to find out. If you went to a metal junction box, you would probably need a ground for that. But PVC conduit and PVC junction boxes are available.

Again, transitioning in the celler, use flex and rigid PVC to get to your breaker panel rather than bending steel conduit. Ideas without eyes, so to speak.

Back up a bit and see what you could comfortably run conduit wise. 3/4 1", 1-1/4? Remember these are ID measurements. The 1-1/4 would be about 1-1/2 in diameter.

The type of conduit also limits the amount of wires your allowed. EMT conduit has thinner walls than PVC conduit, thus it can hold more wires.

You can run romex through conduit, but you don't want too for a variety of reasons.

Remember that drilling holes could prove to be difficult.

Here is a first order look at the conduit thing:
Designing Conduit Runs -- calculating fill factor, sizing conduits, fill factor, designing conduit runs, electrical metallic tubing, 569 compliance, conduit bends.

It doesn't matter if it's a low or high voltage cable. The principle of the calculations are the same. The calcs in the above link assume EMT.

2nd order effects are deratings based on the number of current carrying conductors. Ground doesn't count and neutral SOMETIMES doesn't count.