I can’t compare it to the cad examples but meshmixer is definitely easier to use for small stl edits than blender, especially for things like cutting and keying parts. If you are just trying to make a pin smaller or hole larger, editing the xyz of specific points in blender may be easier depending on shape. Good luck!

I was in a simiar boat, but once I started learning it really took off and I couldn’t find enough things to model/fix! I started with meshmixer, it’s pretty simplified but still somewhat powerful and I think Windows only. Once I found stuff I couldn’t do with it I switched to blender and now I’m much faster with it. I found there are some things each implements better so if having an issue I’ll switch and try something else. I highly recommend picking one and watching youtube videos specific to what you want to change in a model

Edit: you may be able to get by on some of the connectors by lowering flow too, depends on how dialed in your printer is, everyone needs different tolerances

To add, you may not need to worry too much about setting up a firewall if your machine is behind a router/gateway that also has a firewall. There are arguments both ways, I would suggest researching that some. I did it because I could so why not, but I also only have wireguard exposed publicly so it may be over kill

I too read that it didn’t work with docker but that was not my experience on Ubuntu 24.04. Maybe it’s just docker desktop but I had all sorts of other issues with docker desktop and ditched it for plain docker, using lazydocker for an interface. I think one of the issues for outgoing connections at least is that IPs for the containers can change. I don’t remember exactly what my setup is currently but you shouldn’t have an issue opening up just specific ports mapped to a container while having default deny incoming. Not specific to containers but there are a few different Linux commands to get all ports and the processes listening on them, I used them extensively to debug my firewall setup. I can’t remember them either off the top of my head but you should be able to google for your distro.