When I first came across this section, I immediately thought I needed to bop of a Goomba. But how to do this isn't quite clear as you would expect, as the pipe spawns 4 Goombas at a time, there's super-fast conveyor belt and a very little margin of success to pull it off without getting hit, if that's even possible. The proper timing just seems to be too luck-based for me. As a result, I ended up tanking this segment as Super Mario, so I could get past this area.
This is another section where I had to tank through, because there's a very slim opening that no average human could react in time, and the section is too tight to maneuver. By the way, the conveyor belt is slow and 4 Goombas spawn out from a pipe. Also, I'm not sure if I remember correctly, but it is possible to spin jump off from that Thwomp to get past that section pretty easily. If the player doesn't know how to do that, then they might try to do the same way as I did.
This isn't too big of a deal here, but the pipe above is hidden by the camera. When a pipe that spawns something is visible, they'll start spawning in a few seconds. Should that be offscreen, it'll stop operating. The player might be wondering where the heck is the ? Switch, until they board any platform around this area and wait for a short while. At least, that design oversight made the Goomba horde much easier to deal with.
The second Goomba bedroom is accessible by being Propeller Mario via the otherwise inaccessible pipe from the Bowser Jr.'s room. To progress any further, I need to slip through the tiny opening that leads us to another room. As Propeller Mario cannot flutter jump while crouching in this pretty tight section, I had to take a hit from a nearby Goomba, so I could do pull that off as Super Mario. Had this section altered, Propeller Mario still won't break the rest of the stage anyway.