There's an excellent video series by Ben Eater on YouTube where he builds an 8-bit CPU on breadboards. I followed along and built something like it in Logisim, but 16-bit. Logisim wasn't very fast, and I was getting really sick of dragging wires around, so I eventually migrated to Icarus Verilog, then Verilator, and GTKWave to examine traces. I'm one of those developers who uses Windows, so WSL came in really handy for all these.

For the RISC CPU I couldn't tell you exactly what resources I used, it was kind of a blur lol. Basically it was Wikipedia, what I remember from computer architecture class 10 years ago, and a lot of googling, mostly lecture slides from classes I didn't get to take in person. I used ChipVerify for Verilog reference a lot. I can't remember what tutorial I used, but there are plenty out there.