Is this many elbows in a drain line going to cause a massive clog?

That "maze" of white plastic you're describing sounds exactly like a plumbing spider and it’s a red flag for any building inspector. The main issue isn't just how it looks behind the drywall. When you cram a bunch of transitions into one tight spot near the main stack, you usally end up using **short-turn 90s** or tight elbows to make it all fit. Those are literal magnets for hair and soap scum. In a 4-inch stack, you want smooth transitions using 45-degree entries or long-sweep wyes so the water maintains its velocity and acutally clears the pipe. You mentioned going thru the ceiling in multiple spots. If those holes are oversized or if you notched the joists too deeply to make those connections work, you might have a structural problem on top of a plumbing one. Most codes require a certain amount of wood left in the framing to maintain integrity. If you hacked through the center of a load-bearing joist just to get a drain line through, an inspector will likely make you sister those joists before they even look at the PVC. Another thing to worry about is the venting. If all these smaller lines are meeting up in one chaotic junction, there’s a high chance you haven't vented them properly. Every fixture needs air to drain. If you've got three or four lines tied togehter before they hit the stack, the vacuum created by one draining line can pull the water right out of the **P-traps** of the others. You’ll end up with sewer gas smells in the bathroom regardless of how well you patched the ceiling.

Honestly, it sounds like a rip-out is in your future. It's better to fix it now while the walls are open than to have a backup in six months that requires cutting through finished drywall. Look into using a manifold approach or a wet vent setup if the layout allows for it. And please, use long-turn fittings instead of hard 90s wherever you can. It takes up more space, but it actually works.

The part about the joists has me really nervous. I’m planning a similar DIY move and didn’t realize there were strict rules on drilling through the wood framing. Is there a specific limit for how big those holes can be? I'm working with 2x8s and need to run a 2-inch pipe through them.

Also, how do you actualy fit those long-turn elbows inside a standard wall? It seems like they’d be too bulky to stay hidden behind the drywall. I’m trying to avoid making the walls thicker just to get the drainage right.

For those 2x8 joists, keep in mind the 'middle third' rule. A 2-inch pipe requires a hole roughly 2-3/8 inches wide, wich is right at the limit for a 2x8 since you can't exceed 1/3 the joist depth. If you're cutting more than that, you're asking for a bouncy floor or worse.

About the long-turn elbows—yeah, they’re a pain in 2x4 walls. alot of us just fur out the wall or use 2x6 studs for the plumbing run. It sucks to lose two inches of floor space, but it beats having a wall that bulges or a drain that constantly clogs because you squeezed in a tight 90.

Think about what happens when you acutally have to snake those lines. Every extra elbow makes it way harder to get a drain cable trough. If you’ve got a literal maze of turns before you hit the main stack, you’re basically building a trap for yourself. A plumber is going to charge you way more to deal with that headache later, or they'll just tell you to rip the drywall down so they can fix it properly. If you're allready worried about it, just bite the bullet and simplify the run now while it's still open. Future you will be much happier.