I've been reading the other comments, and while people are encouraging, their comments seem a bit too "you HAVE to learn CAD." You definitely don't NEED to know CAD. I made basic parts and modifications in the slicer for nearly a year after I started printing, and it worked really well. However, if you are considering learning a full CAD program, I have two pieces of advice.
First pertains to if you are working with functional parts. Then you are talking about a parametric CAD program (fusion, onshape, FreeCAD, etc.). In this case, I think it's worth learning for you, and it's not as hard as it seems. You say you have SketchUp experience, so I'm assuming you have decent spatial reasoning. I know someone with no tech literacy nor programming experience who learned a CAD program very well in less than a month of following tutorials in her free time. Just give it a try, and it's a skill you'll be happy to have.
If you are working with cosmetic parts like miniatures and helmets, then you might need to use something like Blender. Admittedly, that can be even more challenging than the other CAD programs I mentioned. However, if you spend a few hours learning some basics from YouTube, you should be able to do fundemental things like fixing holes.
Hope this helps. Good luck with your printing endeavors!
Been using it for about five years now. I absolutely love it. But I will say some of these comments make it sound like it's a little easier than it is. I'd say about 80% of your knowledge from Android will transfer over and just work. But the last 20% is a bit of a learning curve, and will take at least a few weeks to get the hang of.
What I recommended to some of my friends that switched is to get the phone and mess around with it for a few weeks before you switch your sim. Then you'll get the hang of things like alternative app stores and sandboxed play services, and you'll figure out what you can and can't do.
I will say the vast majority of things do work easily because of protection compatibility mode and sandboxed play services. But there will be some things that are just more hassle then they're worth. I find keeping a second device, like a tablet, without a custom ROM makes that stuff easier.
And there are some things that seem impossible to get working properly, at least for me. For example, casting to a TV is basically impossible from what I can tell. Also, tap to pay, even for things like tickets doesn't work (although if you have play services, you can use Google wallet for things with barcodes).
Overall, it's totally worth trying out. Just don't set your expectations too high. You're not getting a completely "just works" experience.
As for other custom ROMs, I've tried CalyxOS and LineageOS for MicroG. I didn't find either of them quite as good, but that was many years ago. Maybe they've gotten better.